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/uORBManager_posix.cpp

@@ -94,7 +94,7 @@ orb_advert_t uORB::Manager::orb_advertise_multi(const struct orb_metadata *meta,
   fd = node_open(PUBSUB, meta, data, true, instance, priority);
   if (fd == ERROR) {
     warnx("node_open as advertiser failed.");
-    return ERROR;
+    return 0;
   }
 
   /* get the advertiser handle and close the node */
@@ -102,14 +102,14 @@ orb_advert_t uORB::Manager::orb_advertise_multi(const struct orb_metadata *meta,
   px4_close(fd);
   if (result == ERROR) {
     warnx("px4_ioctl ORBIOCGADVERTISER  failed. fd = %d", fd);
-    return ERROR;
+    return 0;
   }
 
   /* the advertiser must perform an initial publish to initialise the object */
   result = orb_publish(meta, advertiser, data);
   if (result == ERROR) {
     warnx("orb_publish failed");
-    return ERROR;
+    return 0;
   }
 
   return advertiser;