Fix dyncom bugs

The DynCom ARM core was not properly keeping track of the number of instructions executed, and furthermore it incorrectly setting NZCVT register flags.This fixes that, as well as single-step debugging in the Qt GUI. Fixes #176.  
Does the comment need an update for this number, too? (btw, if it does, then it should probably be changed to say "tight_loop" instead of the default value)