relix:  Add process::reset_process_image()
Genie:  Reset the process image in Terminate()

Don't assign an empty one; just reset it.  We need this in order to make
sure that Terminate() doesn't throw exceptions.
Genie:  Axe try block in Process::thread_start()

Nothing we call here throws.
Genie:  Don't specify when the program is released

This statement makes no difference, since (a) full tools call exit() and
terminate before reaching it, and (b) static destructors aren't run in a
microtool or nanotool (since for 68K they must be invoked manually via a
call to __destroy_global_chain() (or exit(), which calls it) and for PPC
they're run by __terminate(), which we didn't install as the termination
routine).
Genie:  Move Run()'s {leave,enter}_system() calls

Move these calls out into thread_start().
Genie:  Cache get_process() result in Exec()
Genie, relix:  Move program from Process to image