extensive orb_advert_t fixes

The calls to orb_advertise were being mishandled throughout the code.
There were ::close() calls on memory pointers, there were checks
against < 0 when it is a pointer to a object and values larger than
0x7ffffffff are valid. Some places orb_advert_t variables were
being initialized as 0 other places as -1.

The orb_advert_t type was changed to uintptr_t so the pointer value
would not be wrapped as a negative number. This was causing a failure
on ARM.

Tests for < 0 were changed to == 0 since a null pointer is the valid
representation for error, or uninitialized.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/modules/attitude_estimator_q/attitude_estimator_q_main.cpp

@@ -114,7 +114,7 @@ private:
 	int		_sensors_sub = -1;
 	int		_params_sub = -1;
 	int		_global_pos_sub = -1;
-	orb_advert_t		_att_pub = -1;
+	orb_advert_t		_att_pub = 0;
 
 	struct {
 		param_t	w_acc;
@@ -327,7 +327,7 @@ void AttitudeEstimatorQ::task_main() {
 		memcpy(&att.R[0], R.data, sizeof(att.R));
 		att.R_valid = true;
 
-		if (_att_pub < 0) {
+		if (_att_pub == 0) {
 			_att_pub = orb_advertise(ORB_ID(vehicle_attitude), &att);
 		} else {
 			orb_publish(ORB_ID(vehicle_attitude), _att_pub, &att);