Now that yacc.c and glr.c both know yysymbol_type_t, convert the
common routines.
* data/skeletons/c.m4 (yydestruct, yy_symbol_value_print)
(yy_symbol_print): Use yysymbol_type_t instead of int.
* data/skeletons/glr.c: Use yySymbol where appropriate.
* data/skeletons/yacc.c (YY_ACCESSING_SYMBOL): New wrapper around
yystos.
Use it.
* tests/local.at (yyreport_syntax_error): Use yysymbol_type_t where
appropriate.