logging: publish a message for PX4_{WARN,ERR} & store them to the ulog file

- ulog file message rate limited to 50Hz
- queuing with size 2
- this replaces the mavlink log message in the ulog
  (but the mavlink warnings & errors still go to the ulog)

src/modules/uORB/Subscription.cpp

@@ -49,6 +49,7 @@
 #include "topics/vehicle_status.h"
 #include "topics/manual_control_setpoint.h"
 #include "topics/mavlink_log.h"
+#include "topics/log_message.h"
 #include "topics/vehicle_local_position_setpoint.h"
 #include "topics/vehicle_local_position.h"
 #include "topics/vehicle_attitude_setpoint.h"
@@ -166,6 +167,7 @@ template class __EXPORT Subscription<position_setpoint_triplet_s>;
 template class __EXPORT Subscription<vehicle_status_s>;
 template class __EXPORT Subscription<manual_control_setpoint_s>;
 template class __EXPORT Subscription<mavlink_log_s>;
+template class __EXPORT Subscription<log_message_s>;
 template class __EXPORT Subscription<vehicle_local_position_setpoint_s>;
 template class __EXPORT Subscription<vehicle_local_position_s>;
 template class __EXPORT Subscription<vehicle_attitude_setpoint_s>;

src/modules/uORB/uORBMain.cpp

@@ -36,6 +36,7 @@
 #include "uORBManager.hpp"
 #include "uORB.h"
 #include "uORBCommon.hpp"
+#include <px4_log.h>
 
 extern "C" { __EXPORT int uorb_main(int argc, char *argv[]); }
 
@@ -78,6 +79,8 @@ uorb_main(int argc, char *argv[])
 			return -errno;
 		}
 
+		px4_log_initialize();
+
 		return OK;
 	}