Log Message:
Update to 0.4.5.

o) Initial support for "disk overlays" has been implemented. This
   enables e.g. simple roll-back of emulated disk contents to a
   previous state.

o) Dyntrans bug fixes; code translations on physical addresses that
   were offset a multiple of 128 MB from each other could either
   cause weird bugs, or translation leaks (leading to unnecessary
   dyntrans cache overflows).

o) Some cleanup: The GDB debugging stub support, some dummy machine
   modes (TS7200, Walnut, PB1000, and Meshcube), and some dummy or
   experimental CPUs (RCA180x and Transputer) have been removed, to
   make the emulator slightly more maintainable.