Initial stab at a context level monitor callback and registration API

src/ctx.hpp

@@ -95,12 +95,17 @@ namespace zmq
         void unregister_endpoints (zmq::socket_base_t *socket_);
         endpoint_t find_endpoint (const char *addr_);
 
+        // Monitoring specific
+        int monitor (zmq_monitor_fn *monitor_);
+        void monitor_event (zmq::socket_base_t *socket_, int event_, ...);
+
         enum {
             term_tid = 0,
             reaper_tid = 1
         };
 
         ~ctx_t ();
+
     private:
 
 
@@ -163,6 +168,9 @@ namespace zmq
         //  Synchronisation of access to context options.
         mutex_t opt_sync;
 
+        // Monitoring callback
+        zmq_monitor_fn *monitor_fn;
+
         ctx_t (const ctx_t&);
         const ctx_t &operator = (const ctx_t&);
     };