[maint] glr.c: add missing cast

[Akim Demaille]

I think I will wrap a 3.5.1.

commit 2cb52c5a91b797eebdae020e4fe56879b5906f43
Author: Akim Demaille <akim.demai...@gmail.com>
Date:   Fri Jan 10 19:24:29 2020 +0100

    glr.c: add missing cast
    
    Reported by psjo.
    Fixes https://github.com/akimd/bison/issues/19.
    
    * data/skeletons/glr.c (yyprocessOneStack): Here.

diff --git a/data/skeletons/glr.c b/data/skeletons/glr.c
index 65744903..e463746e 100644
--- a/data/skeletons/glr.c
+++ b/data/skeletons/glr.c
@@ -1985,7 +1985,8 @@ yyprocessOneStack (yyGLRStack* yystackp, ptrdiff_t yyk,
   while (yystackp->yytops.yystates[yyk] != YY_NULLPTR)
     {
       yyStateNum yystate = yystackp->yytops.yystates[yyk]->yylrState;
-      YY_DPRINTF ((stderr, "Stack %ld Entering state %d\n", yyk, yystate));
+      YY_DPRINTF ((stderr, "Stack %ld Entering state %d\n",
+                   YY_CAST (long, yyk), yystate));
 
       YY_ASSERT (yystate != YYFINAL);