Do not call xmlCleanupParser after parsing news feeds

This function is an aggressive means of releasing memory that may
leave libxml in an unusable state.

extensions/feed-panel/feed-parse.c

@@ -263,7 +263,6 @@ parse_feed (gchar*      data,
                               xerror->message);
         xmlResetLastError ();
     }
-    xmlCleanupParser ();
     xmlMemoryDump ();
 
     return *error ? FALSE : TRUE;