Move the integer-type selection into c.m4

That way, glr.c can use it too.
* data/skeletons/c.m4 (b4_int_type):
Do not special-case ‘char’; it’s not worth the trouble,
as clang complains about char subscripts.
(b4_c99_int_type, b4_c99_int_type_define): New macros,
taken from yacc.c.
* data/skeletons/glr.c: Use b4_int_type_define.
* data/skeletons/yacc.c (b4_int_type): Remove, since there’s
no longer any need to redefine it.
Use b4_c99_int_type_define rather than its body.

data/skeletons/glr.c

@@ -265,6 +265,8 @@ static YYLTYPE yyloc_default][]b4_yyloc_default;])[
 #include <stdlib.h>
 #include <string.h>
 
+]b4_c99_int_type_define[
+
 #ifndef YY_
 # if defined YYENABLE_NLS && YYENABLE_NLS
 #  if ENABLE_NLS