pgsql: Standardize get_whatever_oid functions for other object types.

Log Message:
-----------
Standardize get_whatever_oid functions for other object types.

- Rename TSParserGetPrsid to get_ts_parser_oid.
- Rename TSDictionaryGetDictid to get_ts_dict_oid.
- Rename TSTemplateGetTmplid to get_ts_template_oid.
- Rename TSConfigGetCfgid to get_ts_config_oid.
- Rename FindConversionByName to get_conversion_oid.
- Rename GetConstraintName to get_constraint_oid.
- Add new functions get_opclass_oid, get_opfamily_oid, get_rewrite_oid,
get_rewrite_oid_without_relid, get_trigger_oid, and get_cast_oid.

The name of each function matches the corresponding catalog.

Thanks to KaiGai Kohei for the review.

Modified Files:
--------------
pgsql/contrib/tsearch2:
tsearch2.c (r1.12 -> r1.13)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/tsearch2/tsearch2.c?r1=1.12&r2=1.13)
pgsql/contrib/unaccent:
unaccent.c (r1.5 -> r1.6)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/unaccent/unaccent.c?r1=1.5&r2=1.6)
pgsql/src/backend/catalog:
namespace.c (r1.126 -> r1.127)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/namespace.c?r1=1.126&r2=1.127)
pg_constraint.c (r1.53 -> r1.54)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/catalog/pg_constraint.c?r1=1.53&r2=1.54)
pgsql/src/backend/commands:
comment.c (r1.116 -> r1.117)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/comment.c?r1=1.116&r2=1.117)
conversioncmds.c (r1.41 -> r1.42)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/conversioncmds.c?r1=1.41&r2=1.42)
functioncmds.c (r1.118 -> r1.119)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/functioncmds.c?r1=1.118&r2=1.119)
opclasscmds.c (r1.70 -> r1.71)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/opclasscmds.c?r1=1.70&r2=1.71)
trigger.c (r1.263 -> r1.264)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/trigger.c?r1=1.263&r2=1.264)
tsearchcmds.c (r1.20 -> r1.21)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/commands/tsearchcmds.c?r1=1.20&r2=1.21)
pgsql/src/backend/parser:
parse_utilcmd.c (r2.41 -> r2.42)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/parser/parse_utilcmd.c?r1=2.41&r2=2.42)
pgsql/src/backend/rewrite:
rewriteSupport.c (r1.69 -> r1.70)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/rewrite/rewriteSupport.c?r1=1.69&r2=1.70)
pgsql/src/backend/tsearch:
dict_thesaurus.c (r1.16 -> r1.17)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tsearch/dict_thesaurus.c?r1=1.16&r2=1.17)
wparser.c (r1.12 -> r1.13)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/tsearch/wparser.c?r1=1.12&r2=1.13)
pgsql/src/backend/utils/adt:
regproc.c (r1.113 -> r1.114)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/regproc.c?r1=1.113&r2=1.114)
tsvector_op.c (r1.26 -> r1.27)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tsvector_op.c?r1=1.26&r2=1.27)
pgsql/src/backend/utils/cache:
ts_cache.c (r1.12 -> r1.13)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/cache/ts_cache.c?r1=1.12&r2=1.13)
pgsql/src/include/catalog:
namespace.h (r1.63 -> r1.64)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/namespace.h?r1=1.63&r2=1.64)
pg_constraint.h (r1.39 -> r1.40)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/catalog/pg_constraint.h?r1=1.39&r2=1.40)
pgsql/src/include/commands:
defrem.h (r1.103 -> r1.104)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/defrem.h?r1=1.103&r2=1.104)
trigger.h (r1.80 -> r1.81)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/commands/trigger.h?r1=1.80&r2=1.81)
pgsql/src/include/rewrite:
rewriteSupport.h (r1.32 -> r1.33)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/rewrite/rewriteSupport.h?r1=1.32&r2=1.33)