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/collationcmds.c

@@ -38,7 +38,7 @@
  * CREATE COLLATION
  */
 ObjectAddress
-DefineCollation(List *names, List *parameters)
+DefineCollation(ParseState *pstate, List *names, List *parameters)
 {
 	char	   *collName;
 	Oid			collNamespace;
@@ -78,7 +78,8 @@ DefineCollation(List *names, List *parameters)
 			ereport(ERROR,
 					(errcode(ERRCODE_SYNTAX_ERROR),
 					 errmsg("collation attribute \"%s\" not recognized",
-							defel->defname)));
+							defel->defname),
+					 parser_errposition(pstate, defel->location)));
 			break;
 		}