add sessions since start up to heartbeat event

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@12472 d0543943-73ff-0310-b7d9-9358b9ac24b2

src/switch_core.c

@@ -75,6 +75,7 @@ static void send_heartbeat(void)
 
 		switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Session-Count", "%u", switch_core_session_count());
 		switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Session-Per-Sec", "%u", runtime.sps);
+		switch_event_add_header(event, SWITCH_STACK_BOTTOM, "Session-Since-Startup", "%" SWITCH_SIZE_T_FMT, switch_core_session_id() - 1);
 		switch_event_fire(&event);
 	}
 }