glr.c: remove (broken) support for YYPRINT.

YYPRINT uses yytoknum which glr does not define.  Since YYPRINT
is considered obsolete, and did not work, don't fix its support,
remove it from glr.c.

* data/c.m4 (yy_symbol_value_print): Use YYPRINT only for yacc.c.
* TODO: Done.

data/c.m4

@@ -485,12 +485,15 @@ m4_ifset([b4_parse_param], [, b4_parse_param]))[
 {
 ]b4_parse_param_use([yyoutput], [yylocationp])[
   if (!yyvaluep)
-    return;
-# ifdef YYPRINT
+    return;]
+dnl glr.c does not feature yytoknum.
+m4_if(b4_skeleton, ["yacc.c"],
+[[# ifdef YYPRINT
   if (yytype < YYNTOKENS)
     YYPRINT (yyoutput, yytoknum[yytype], *yyvaluep);
 # endif
-  switch (yytype)
+]])dnl
+[  switch (yytype)
     {
 ]b4_symbol_foreach([b4_symbol_printer])dnl
 [      default: