Merge 'maint'

* upstream/maint:
  maint: post-release administrivia
  version 3.6.4
  glr.cc: don't leak glr.c/glr.cc scaffolding to the user

Some fixes were needed to adjust to recent changes in glr.cc and
glr.c.

* data/skeletons/glr.cc: Stop messing with the user's epilogue to
insert glr.cc code.  We need that code to be inserted _before_ the
user's epilogue, not after.  So define b4_glr_cc_pre_epilogue.
* data/skeletons/glr.c: Use it.

TODO

@@ -12,6 +12,9 @@ list_get_end (gl_list_t list)
   return res;
 }
 
+** glr.cc
+Get rid of global_tokens_and_yystype.
+
 ** Bistromathic
 - Hitting tab on a line with a syntax error is ugly
 
@@ -149,6 +152,9 @@ Les catégories d'avertissements incluent :
 Line -1 and -3 should mention CATEGORIE, not CATEGORY.
 
 * Bison 3.8
+** Rewrite glr.cc
+Get rid of scaffolding in glr.c.
+
 ** Unit rules / Injection rules (Akim Demaille)
 Maybe we could expand unit rules (or "injections", see
 https://homepages.cwi.nl/~daybuild/daily-books/syntax/2-sdf/sdf.html), i.e.,