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/uORB/uORBTest_UnitTest.hpp

@@ -98,7 +98,7 @@ int uORBTest::UnitTest::latency_test(orb_id_t T, bool print)
   t.val = 308;
   t.time = hrt_absolute_time();
 
-  int pfd0 = orb_advertise(T, &t);
+  orb_advert_t pfd0 = orb_advertise(T, &t);
 
   char * const args[1] = { NULL };
 
@@ -128,8 +128,6 @@ int uORBTest::UnitTest::latency_test(orb_id_t T, bool print)
     usleep(1000);
   }
 
-  px4_close(pfd0);
-
   if (pubsub_task < 0) {
     return test_fail("failed launching task");
   }