pgsql: Fix multiple minor infelicities in aclchk.c error reports.

Fix multiple minor infelicities in aclchk.c error reports.

pg_type_aclmask reported the wrong type's OID when complaining that
it could not find a type's typelem. It also failed to provide a
suitable errcode when the initially given OID doesn't exist (which
is a user-facing error, since that OID can be user-specified).
pg_foreign_data_wrapper_aclmask and pg_foreign_server_aclmask likewise
lacked errcode specifications. Trivial cosmetic adjustments too.

The wrong-type-OID problem was reported by Petru-Florin Mihancea in
bug #14186; the other issues noted by me while reading the code.
These errors all seem to be aboriginal in the respective routines, so
back-patch as necessary.

Report: <20160613163159(dot)5798(dot)52928(at)wrigleys(dot)postgresql(dot)org>

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/cd05539ec7f5eba2c1370447f27d2343c96bbeee

Modified Files
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src/backend/catalog/aclchk.c | 23 ++++++++++++++---------
1 file changed, 14 insertions(+), 9 deletions(-)