glr: allow spaces between "%?" and "{" in predicates

Reported by Rici Lake.
http://lists.gnu.org/archive/html/bug-bison/2013-10/msg00004.html
http://stackoverflow.com/questions/19330171/

* src/scan-gram.l: Do not try to be too smart when diagnosing invalid
directives.
* tests/glr-regression.at (Predicates): New test.

src/scan-gram.l

@@ -266,7 +266,7 @@ eqopt    ([[:space:]]*=)?
   "%pure"[-_]"parser"               DEPRECATED("%pure-parser");
   "%token"[-_]"table"               DEPRECATED("%token-table");
 
-  "%"{id}|"%"{notletter}([[:graph:]])+ {
+  "%"{id} {
     complain (loc, complaint, _("invalid directive: %s"), quote (yytext));
   }