MXS-1220: Add threads resource

The threads are now a REST API resource exposed via the /maxscale/threads
resource collection.

server/core/maxscale/worker.hh

@@ -159,6 +159,16 @@ public:
      */
     static int64_t get_one_statistic(POLL_STAT what);
 
+    /**
+     * Return this worker's statistics.
+     *
+     * @return Local statistics for this worker.
+     */
+    const STATISTICS& get_local_statistics() const
+    {
+        return m_statistics;
+    }
+
     /**
      * Add a file descriptor to the epoll instance of the worker.
      *