Cannot trace error location when %glr-parser and %pure-parser are used together.

[Slava Savitsky]

   Here's a problem: for a grammar with both %glr-parser and %pure-parser
   declarations a location-aware error reporting function cannot be used.

   Usually to track the error position one defines "yyerror(msg)" to
   "print_error(message, &yylval, yychar)", right? In the pure parser
   "yylval" becomes "yystackp->yylval". The problem is, yyerror(YY_(msg))
   is called from the "reportAmbiguity" function which does not take the
   "yystackp" argument.

   A possible fix would be:

   --- /usr/share/bison/glr.cssss 2012-12-14 20:07:40.516065313 +0400
   +++ /usr/share/bison/glr.csss 2012-12-14 19:49:35.600065872 +0400
   @@ -1788,8 +1788,7 @@
   s#endif
   s
   s/*ARGSUSED*/ static YYRESULTTAG
   -yyreportAmbiguity (yyGLRStack* yystackp,
   -ssssssssssssssssss yySemanticOption* yyx0,
   +yyreportAmbiguity (yySemanticOption* yyx0,
   ssss sss ss yySemanticOption* yyx1]b4_pure_formals[)
   s{
   ss YYUSE (yyx0);
   @@ -1900,7 +1899,7 @@
   ssss sss {
   ssss sss case 0:
   ssss sssss yyresolveLocations (yys, 1, yystackp]b4_user_args[);
   -sss sssss return yyreportAmbiguity (yystackp, yybest,
   yyp]b4_pure_args[);
   +sss sssss return yyreportAmbiguity (yybest, yyp]b4_pure_args[);
   ssss sssss break;
   ssss sss case 1:
   ssss sssss yymerge = yytrue;

   Slava Savitskiy.