pgsql: Update documentation on may/can/might: Standard English uses

Log Message:
-----------
Update documentation on may/can/might:

Standard English uses "may", "can", and "might" in different ways:

may - permission, "You may borrow my rake."

can - ability, "I can lift that log."

might - possibility, "It might rain today."

Unfortunately, in conversational English, their use is often mixed, as
in, "You may use this variable to do X", when in fact, "can" is a better
choice. Similarly, "It may crash" is better stated, "It might crash".

Also update two error messages mentioned in the documenation to match.

Modified Files:
--------------
pgsql/doc/src/sgml:
advanced.sgml (r1.52 -> r1.53)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/advanced.sgml.diff?r1=1.52&r2=1.53)
arch-dev.sgml (r2.28 -> r2.29)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/arch-dev.sgml.diff?r1=2.28&r2=2.29)
array.sgml (r1.54 -> r1.55)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/array.sgml.diff?r1=1.54&r2=1.55)
backup.sgml (r2.95 -> r2.96)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/backup.sgml.diff?r1=2.95&r2=2.96)
bki.sgml (r1.19 -> r1.20)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/bki.sgml.diff?r1=1.19&r2=1.20)
catalogs.sgml (r2.143 -> r2.144)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml.diff?r1=2.143&r2=2.144)
charset.sgml (r2.80 -> r2.81)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/charset.sgml.diff?r1=2.80&r2=2.81)
client-auth.sgml (r1.96 -> r1.97)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/client-auth.sgml.diff?r1=1.96&r2=1.97)
config.sgml (r1.106 -> r1.107)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml.diff?r1=1.106&r2=1.107)
cvs.sgml (r1.39 -> r1.40)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/cvs.sgml.diff?r1=1.39&r2=1.40)
datatype.sgml (r1.188 -> r1.189)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datatype.sgml.diff?r1=1.188&r2=1.189)
datetime.sgml (r2.55 -> r2.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/datetime.sgml.diff?r1=2.55&r2=2.56)
ddl.sgml (r1.71 -> r1.72)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ddl.sgml.diff?r1=1.71&r2=1.72)
diskusage.sgml (r1.17 -> r1.18)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/diskusage.sgml.diff?r1=1.17&r2=1.18)
dml.sgml (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/dml.sgml.diff?r1=1.14&r2=1.15)
docguide.sgml (r1.68 -> r1.69)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/docguide.sgml.diff?r1=1.68&r2=1.69)
ecpg.sgml (r1.77 -> r1.78)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ecpg.sgml.diff?r1=1.77&r2=1.78)
errcodes.sgml (r1.21 -> r1.22)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/errcodes.sgml.diff?r1=1.21&r2=1.22)
extend.sgml (r1.32 -> r1.33)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/extend.sgml.diff?r1=1.32&r2=1.33)
external-projects.sgml (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/external-projects.sgml.diff?r1=1.14&r2=1.15)
features.sgml (r2.25 -> r2.26)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/features.sgml.diff?r1=2.25&r2=2.26)
func.sgml (r1.355 -> r1.356)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.355&r2=1.356)
gin.sgml (r2.8 -> r2.9)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/gin.sgml.diff?r1=2.8&r2=2.9)
gist.sgml (r1.27 -> r1.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/gist.sgml.diff?r1=1.27&r2=1.28)
indexam.sgml (r2.20 -> r2.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indexam.sgml.diff?r1=2.20&r2=2.21)
indices.sgml (r1.67 -> r1.68)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/indices.sgml.diff?r1=1.67&r2=1.68)
information_schema.sgml (r1.29 -> r1.30)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/information_schema.sgml.diff?r1=1.29&r2=1.30)
installation.sgml (r1.278 -> r1.279)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/installation.sgml.diff?r1=1.278&r2=1.279)
intro.sgml (r1.31 -> r1.32)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/intro.sgml.diff?r1=1.31&r2=1.32)
libpq.sgml (r1.222 -> r1.223)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml.diff?r1=1.222&r2=1.223)
lobj.sgml (r1.42 -> r1.43)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/lobj.sgml.diff?r1=1.42&r2=1.43)
maintenance.sgml (r1.67 -> r1.68)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/maintenance.sgml.diff?r1=1.67&r2=1.68)
manage-ag.sgml (r2.51 -> r2.52)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/manage-ag.sgml.diff?r1=2.51&r2=2.52)
monitoring.sgml (r1.43 -> r1.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml.diff?r1=1.43&r2=1.44)
mvcc.sgml (r2.65 -> r2.66)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/mvcc.sgml.diff?r1=2.65&r2=2.66)
nls.sgml (r1.14 -> r1.15)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/nls.sgml.diff?r1=1.14&r2=1.15)
perform.sgml (r1.60 -> r1.61)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/perform.sgml.diff?r1=1.60&r2=1.61)
planstats.sgml (r1.7 -> r1.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/planstats.sgml.diff?r1=1.7&r2=1.8)
plperl.sgml (r2.60 -> r2.61)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plperl.sgml.diff?r1=2.60&r2=2.61)
plpgsql.sgml (r1.103 -> r1.104)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpgsql.sgml.diff?r1=1.103&r2=1.104)
plpython.sgml (r1.36 -> r1.37)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/plpython.sgml.diff?r1=1.36&r2=1.37)
pltcl.sgml (r2.43 -> r2.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/pltcl.sgml.diff?r1=2.43&r2=2.44)
postgres.sgml (r1.80 -> r1.81)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/postgres.sgml.diff?r1=1.80&r2=1.81)
problems.sgml (r2.27 -> r2.28)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/problems.sgml.diff?r1=2.27&r2=2.28)
protocol.sgml (r1.66 -> r1.67)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/protocol.sgml.diff?r1=1.66&r2=1.67)
queries.sgml (r1.41 -> r1.42)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/queries.sgml.diff?r1=1.41&r2=1.42)
query.sgml (r1.48 -> r1.49)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/query.sgml.diff?r1=1.48&r2=1.49)
reference.sgml (r1.61 -> r1.62)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/reference.sgml.diff?r1=1.61&r2=1.62)
regress.sgml (r1.55 -> r1.56)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/regress.sgml.diff?r1=1.55&r2=1.56)
release.sgml (r1.491 -> r1.492)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/release.sgml.diff?r1=1.491&r2=1.492)
rowtypes.sgml (r2.7 -> r2.8)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/rowtypes.sgml.diff?r1=2.7&r2=2.8)
rules.sgml (r1.48 -> r1.49)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/rules.sgml.diff?r1=1.48&r2=1.49)
runtime.sgml (r1.374 -> r1.375)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/runtime.sgml.diff?r1=1.374&r2=1.375)
sources.sgml (r2.20 -> r2.21)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/sources.sgml.diff?r1=2.20&r2=2.21)
spi.sgml (r1.49 -> r1.50)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/spi.sgml.diff?r1=1.49&r2=1.50)
sql.sgml (r1.43 -> r1.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/sql.sgml.diff?r1=1.43&r2=1.44)
start.sgml (r1.43 -> r1.44)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/start.sgml.diff?r1=1.43&r2=1.44)
storage.sgml (r1.13 -> r1.14)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/storage.sgml.diff?r1=1.13&r2=1.14)
syntax.sgml (r1.111 -> r1.112)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/syntax.sgml.diff?r1=1.111&r2=1.112)
trigger.sgml (r1.47 -> r1.48)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/trigger.sgml.diff?r1=1.47&r2=1.48)
typeconv.sgml (r1.48 -> r1.49)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/typeconv.sgml.diff?r1=1.48&r2=1.49)
user-manag.sgml (r1.37 -> r1.38)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/user-manag.sgml.diff?r1=1.37&r2=1.38)
wal.sgml (r1.42 -> r1.43)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/wal.sgml.diff?r1=1.42&r2=1.43)
xaggr.sgml (r1.33 -> r1.34)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xaggr.sgml.diff?r1=1.33&r2=1.34)
xfunc.sgml (r1.122 -> r1.123)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xfunc.sgml.diff?r1=1.122&r2=1.123)
xindex.sgml (r1.56 -> r1.57)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xindex.sgml.diff?r1=1.56&r2=1.57)
xoper.sgml (r1.38 -> r1.39)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xoper.sgml.diff?r1=1.38&r2=1.39)
xplang.sgml (r1.32 -> r1.33)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xplang.sgml.diff?r1=1.32&r2=1.33)
pgsql/src/backend/parser:
parse_func.c (r1.191 -> r1.192)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_func.c.diff?r1=1.191&r2=1.192)
parse_oper.c (r1.91 -> r1.92)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_oper.c.diff?r1=1.91&r2=1.92)