whb: Add ability to remove logging functions

* WHBRemoveLogHandler will look through the "registry" of logging
functions, and will set the entry to NULL if it matches what the user
passes.
* WHBLogUdpDeinit will correctly close the socket and shut down the
socket library in addition to removing its entry in the registry.

samples/gx2/triangle/src/main.c

@@ -116,5 +116,6 @@ exit:
    WHBUnmountSdCard();
    WHBGfxShutdown();
    WHBProcShutdown();
+   WHBLogUdpDeinit();
    return result;
 }