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.

src/backend/utils/adt/tsvector_op.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsvector_op.c,v 1.26 2010/01/02 16:57:55 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/adt/tsvector_op.c,v 1.27 2010/08/05 15:25:35 rhaas Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1326,7 +1326,7 @@ tsvector_update_trigger(PG_FUNCTION_ARGS, bool config_column)
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("text search configuration name \"%s\" must be schema-qualified",
 							trigger->tgargs[1])));
-		cfgId = TSConfigGetCfgid(names, false);
+		cfgId = get_ts_config_oid(names, false);
 	}
 
 	/* initialize parse state */