Rename STOP command to EXIT, introduce ATEXIT, this gives better
control over the exit of the stub. Add stmp implementation.
Change-Id: I45442c8b88b9330d12ef439417ca5ffa1520477a
Completely rewrite the Mafile, properly put the usb driver in its
own file and the target specific files in a subdirectory.
Change-Id: Iaeee0128e021d5dad76b4d6035a63e33e2d946c1
