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/navigator/geofence.cpp

@@ -69,7 +69,7 @@ static const int ERROR = -1;
 
 Geofence::Geofence() :
 	SuperBlock(NULL, "GF"),
-	_fence_pub(-1),
+	_fence_pub(0),
 	_home_pos{},
 	_home_pos_set(false),
 	_last_horizontal_range_warning(0),
@@ -317,7 +317,7 @@ Geofence::addPoint(int argc, char *argv[])
 void
 Geofence::publishFence(unsigned vertices)
 {
-	if (_fence_pub == -1) {
+	if (_fence_pub == 0) {
 		_fence_pub = orb_advertise(ORB_ID(fence), &vertices);
 
 	} else {