Halting

`ADD PC, -1` (`0x8382`) will be treated as a 'halt' instruction. While halted, no execution will occur but time warp is unlimited. If an interrupt occurs, time warp is throttled, execution continues at the interrupt address, and if the CPU halts again, time warp is restored to what it previously was.

The display window will also show *Powered Off*, *Halted* or *Clock Speed* depending on the CPUs current state.

Note, that due to SirCmpwn/Tomato#42, interrupts due to the generic clock device won't work properly.