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/systemcmds/motor_test/motor_test.c

@@ -59,7 +59,7 @@ __EXPORT int motor_test_main(int argc, char *argv[]);
 static void motor_test(unsigned channel, float value);
 static void usage(const char *reason);
 
-static orb_advert_t _test_motor_pub;
+static orb_advert_t _test_motor_pub = 0;
 
 void motor_test(unsigned channel, float value)
 {