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/vtol_att_control/vtol_att_control_main.cpp

@@ -230,10 +230,10 @@ VtolAttitudeControl::VtolAttitudeControl() :
 	_battery_status_sub(-1),
 
 	//init publication handlers
-	_actuators_0_pub(-1),
-	_actuators_1_pub(-1),
-	_vtol_vehicle_status_pub(-1),
-	_v_rates_sp_pub(-1),
+	_actuators_0_pub(0),
+	_actuators_1_pub(0),
+	_vtol_vehicle_status_pub(0),
+	_v_rates_sp_pub(0),
 
 	_loop_perf(perf_alloc(PC_ELAPSED, "vtol_att_control")),
 	_nonfinite_input_perf(perf_alloc(PC_COUNT, "vtol att control nonfinite input"))