Avoid variables for format strings, as then GCC cannot check them.
show_sub_messages should call show_sub_message.
+** m4 names
+b4_shared_declarations is no longer what it is. Make it
+b4_parser_declaration for instance.
+
+** glr.cc: %defines
+it should not be mandatory.
+
+** stack.hh
+Get rid of it. The original idea is nice, but actually it makes
+the code harder to follow, and uselessly different from the other
+skeletons.
+
** Variable names.
What should we name `variant' and `lex_symbol'?