pgsql: Clean up SQL emitted by psql/describe.c.

Clean up SQL emitted by psql/describe.c.

Fix assorted places that had not bothered with the convention of
prefixing catalog and function names with "pg_catalog.". That
could possibly result in query failure when running with a nondefault
search_path. Also fix two places that weren't quoting OID literals.
I think the latter hasn't mattered much since about 7.3, but it's still
a bad idea to be doing it in 99 places and not in 2 others.

Also remove a useless EXISTS sub-select that someone had stuck into
describeOneTableDetails' queries for child tables. We just got the OID
out of pg_class, so I hardly see how checking that it exists in pg_class
was doing anything helpful.

In passing, try to improve the emitted formatting of a couple of
these queries, though I didn't work really hard on that. And merge
unnecessarily duplicative coding in some other places.

Much of this was new in HEAD, but some was quite old; back-patch
as appropriate.

Branch
------
REL9_2_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/51b76f974176b7e517b7836f56e360edbb6fd2fd

Modified Files
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src/bin/psql/describe.c | 66 ++++++++++++++++++++++++-------------------------
1 file changed, 33 insertions(+), 33 deletions(-)