pgsql: Change the notation for calling functions with named parameters

Log Message:
-----------
Change the notation for calling functions with named parameters from
"val AS name" to "name := val", as per recent discussion.

This patch catches everything in the original named-parameters patch,
but I'm not certain that no other dependencies snuck in later (grepping
the source tree for all uses of AS soon proved unworkable).

In passing I note that we've dropped the ball at least once on keeping
ecpg's lexer (as opposed to parser) in sync with the backend. It would
be a good idea to go through all of pgc.l and see if it's in sync now.
I didn't attempt that at the moment.

Modified Files:
--------------
pgsql/doc/src/sgml:
syntax.sgml (r1.144 -> r1.145)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/syntax.sgml?r1=1.144&r2=1.145)
xfunc.sgml (r1.148 -> r1.149)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/xfunc.sgml?r1=1.148&r2=1.149)
pgsql/src/backend/parser:
gram.y (r2.711 -> r2.712)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/gram.y?r1=2.711&r2=2.712)
parse_func.c (r1.223 -> r1.224)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_func.c?r1=1.223&r2=1.224)
scan.l (r1.166 -> r1.167)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/scan.l?r1=1.166&r2=1.167)
pgsql/src/backend/utils/adt:
ruleutils.c (r1.325 -> r1.326)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/ruleutils.c?r1=1.325&r2=1.326)
pgsql/src/bin/psql:
psqlscan.l (r1.33 -> r1.34)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/bin/psql/psqlscan.l?r1=1.33&r2=1.34)
pgsql/src/interfaces/ecpg/preproc:
parse.pl (r1.7 -> r1.8)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/parse.pl?r1=1.7&r2=1.8)
pgc.l (r1.173 -> r1.174)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/pgc.l?r1=1.173&r2=1.174)
pgsql/src/test/regress/expected:
polymorphism.out (r1.22 -> r1.23)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/polymorphism.out?r1=1.22&r2=1.23)
pgsql/src/test/regress/sql:
polymorphism.sql (r1.13 -> r1.14)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/sql/polymorphism.sql?r1=1.13&r2=1.14)