Don't pass oidvector by value.

Since the structure ends with a flexible array, doing so truncates any
vector having more than one element.  New in 9.3, so no back-patch.

src/backend/commands/functioncmds.c

@@ -1626,18 +1626,18 @@ DropCastById(Oid castOid)
  */
 void
 IsThereFunctionInNamespace(const char *proname, int pronargs,
-						   oidvector proargtypes, Oid nspOid)
+						   oidvector *proargtypes, Oid nspOid)
 {
 	/* check for duplicate name (more friendly than unique-index failure) */
 	if (SearchSysCacheExists3(PROCNAMEARGSNSP,
 							  CStringGetDatum(proname),
-							  PointerGetDatum(&proargtypes),
+							  PointerGetDatum(proargtypes),
 							  ObjectIdGetDatum(nspOid)))
 		ereport(ERROR,
 				(errcode(ERRCODE_DUPLICATE_FUNCTION),
 				 errmsg("function %s already exists in schema \"%s\"",
 						funcname_signature_string(proname, pronargs,
-												  NIL, proargtypes.values),
+												  NIL, proargtypes->values),
 						get_namespace_name(nspOid))));
 }