Fix push parsing memory leak reported by Brandon Lucia at

<http://lists.gnu.org/archive/html/bug-bison/2007-07/msg00032.html>.
* THANKS: Add Brandon Lucia.
* data/push.c (yypstate_delete): Free the stack if it was reallocated
but the parse never completed and thus freed it.
* tests/Makefile.am (TESTSUITE_AT): Add push.at.
* tests/testsuite.at: Include push.at.
* test/push.at: New.
(Push Parsing: Memory Leak for Early Deletion): New test case.

data/push.c

@@ -1124,6 +1124,12 @@ b4_push_if(
 ]b4_c_function_def([[yypstate_delete]], [[void]],
                    [[[yypstate *yyps]], [[yyps]]])[
 {
+#ifndef yyoverflow
+  /* If the stack was reallocated but the parse did not complete, then the
+     stack still needs to be freed.  */
+  if (!yyps->yynew && yyps->yyss != yyps->yyssa)
+    YYSTACK_FREE (yyps->yyss);
+#endif
   free (yyps);
 }