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/bottle_drop/bottle_drop.cpp

@@ -180,7 +180,7 @@ BottleDrop::BottleDrop() :
 	_command {},
 	_global_pos {},
 	ref {},
-	_actuator_pub(-1),
+	_actuator_pub(0),
 	_actuators {},
 	_drop_approval(false),
 	_doors_opened(0),
@@ -190,7 +190,7 @@ BottleDrop::BottleDrop() :
 	_drop_position {},
 	_drop_state(DROP_STATE_INIT),
 	_onboard_mission {},
-	_onboard_mission_pub(-1)
+	_onboard_mission_pub(0)
 {
 }