fixed a memory leak (xmlXPathLangFunction) reported on the list by Mike

* xpath.c: fixed a memory leak (xmlXPathLangFunction) reported
  on the list by Mike Hommey
diff --git a/xpath.c b/xpath.c
index 4d061cb..881e936 100644
--- a/xpath.c
+++ b/xpath.c
@@ -7022,6 +7022,7 @@
         ret = 1;
     }
 not_equal:
+    xmlFree((void *)theLang);
     xmlXPathFreeObject(val);
     valuePush(ctxt, xmlXPathNewBoolean(ret));
 }