pgsql: Improve documentation for pg_largeobject changes.

Log Message:
-----------
Improve documentation for pg_largeobject changes.

Rewrite the documentation in more idiomatic English, and in the process make
it somewhat more succinct. Move the discussion of specific large object
privileges out of the "server-side functions" section, where it certainly
doesn't belong, and into "implementation features". That might not be
exactly right either, but it doesn't seem worth creating a new section for
this amount of information. Fix a few spelling and layout problems, too.

Modified Files:
--------------
pgsql/doc/src/sgml:
catalogs.sgml (r2.213 -> r2.214)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/catalogs.sgml?r1=2.213&r2=2.214)
config.sgml (r1.237 -> r1.238)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/config.sgml?r1=1.237&r2=1.238)
lobj.sgml (r1.50 -> r1.51)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/lobj.sgml?r1=1.50&r2=1.51)
pgsql/doc/src/sgml/ref:
grant.sgml (r1.80 -> r1.81)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/ref/grant.sgml?r1=1.80&r2=1.81)