Coverity issue CID #167

Event alloc_fn: Called allocation function "metacompile" [model]
Event var_assign: Assigned variable "gr" to storage returned from "metacompile"
		gr = metacompile(n);
Event pass_arg: Variable "gr" not freed or pointed-to in function "maketables" [model]
		g = maketables(gr);
  		translatelabels(g);
  		addfirstsets(g);
Event leaked_storage: Returned without freeing storage "gr"
		return g;

Parser/pgen.c

@@ -667,6 +667,7 @@ pgen(node *n)
 	g = maketables(gr);
 	translatelabels(g);
 	addfirstsets(g);
+	PyObject_FREE(gr);
 	return g;
 }