Changes from Jonathan Riehl to allow his pgen extension (PEP 269) to

work.  This includes some more code that used to be part of pgen in
the main parser; I'm okay with that.  I'll see if the Windows build
needs work next.

Parser/metagrammar.c

@@ -151,3 +151,9 @@ meta_grammar(void)
 {
 	return &_PyParser_Grammar;
 }
+
+grammar *
+Py_meta_grammar(void)
+{
+  return meta_grammar();
+}