Fix CMP, CPX, CPY to compute the carry bit correctly. Fix ROR so that it shifts in carry into bit 7 correctly.
Debugger: 'l' to toggle logging operations (because it's slow); add support for breakpoints (software and hardware).
Fix many CPU bugs

* Indexed indirect (zp,x) now wraps high byte on zero page
* Indirect indexed (zp),y now wraps high byte on zero page
* BIT correctly copies bits 6 and 7 from memory value to P
* CPX and CPY set carry bit correctly
* SBC no longer off by 1
* PLP correctly updates P from stack