Fixed a bug where an extra 4 ticks is spent on CB prefixed instructions on a Z80.
Fixed a bug where an extra 4 ticks is spent on CB prefixed instructions on a Z80.

* What is really cool about this bug is that it was found after using this CPU as a reference for another Z80 CPU implementation I am working on. After detecting a mismatch in my CPU state after execution of some CB prefixed instruction on my 2 CPU, I realized the bug was on the reference CPU, not the one I was implementing.

boucha05/ManyEmu,boucha05/ManyEmu