Merge mysql.com:/M50/clone-5.0 into mysql.com:/M51/clone-5.1

sql/log.cc:
  Auto merged

sql/log.cc

@@ -3122,7 +3122,11 @@ bool MYSQL_LOG::write(THD *thd, IO_CACHE *cache, Log_event *commit_event)
       rotate binlog, if necessary.
     */
     if (commit_event->get_type_code() == XID_EVENT)
-      thread_safe_increment(prepared_xids, &LOCK_prep_xids);
+    {
+      pthread_mutex_lock(&LOCK_prep_xids);
+      prepared_xids++;
+      pthread_mutex_unlock(&LOCK_prep_xids);
+    }
     else
       rotate_and_purge(RP_LOCK_LOG_IS_ALREADY_LOCKED);
   }