(YYRHSLOC): Don't have two definitions, one for

(YYRHSLOC): Don't have two definitions, one for
the normal case and one for the error case.  Just use the
first one uniformly.  Problem reported by Frank Heckenbach.
(YYLLOC_DEFAULT): Use the conventions of yacc.c, so we can
use exactly the same macro in both places.
(yyerror_range): Now of type yyGLRStackItem, not YYLTYPE,
so that the normal-case YYRHSLOC works for the error case too.
All uses changed.