Work around GCC 4.8 false alarms without casts

* data/skeletons/yacc.c (yyparse):
Initialize yyes_capacity with a signed expression.
* tests/local.at (AT_YYLEX_DEFINE(c)):
Use enum to avoid cast.

tests/local.at

@@ -558,7 +558,7 @@ static
   static int toknum = 0;
   int res;
   ]AT_USE_LEX_ARGS[
-  int input_elts = (int) (sizeof input / sizeof input[0]);
+  enum { input_elts = sizeof input / sizeof input[0] };
   (void) input_elts;
   assert (0 <= toknum && toknum < input_elts);
   res = input[toknum++];