Add location field to DefElem

Add a location field to the DefElem struct, used to parse many utility
commands.  Update various error messages to supply error position
information.

To propogate the error position information in a more systematic way,
create a ParseState in standard_ProcessUtility() and pass that to
interested functions implementing the utility commands.  This seems
better than passing the query string and then reassembling a parse state
ad hoc, which violates the encapsulation of the ParseState type.

Reviewed-by: Pavel Stehule <pavel.stehule@gmail.com>

src/backend/commands/define.c

@@ -319,12 +319,3 @@ defGetTypeLength(DefElem *def)
 					def->defname, defGetString(def))));
 	return 0;					/* keep compiler quiet */
 }
-
-/*
- * Create a DefElem setting "oids" to the specified value.
- */
-DefElem *
-defWithOids(bool value)
-{
-	return makeDefElem("oids", (Node *) makeInteger(value));
-}