Changes
/* Oddities */
* Conditional jumps are only 8-bit relative. And unconditional jumps are only 16-bit absolute.
* the Z80 pre-decrements on PUSH and post-increments on POP, while the 6502 post-decrements on PHA and pre-increments on PLA, making them behave in opposite ways.
* ADC is the only command for addition. To perform an addition without carry, the carry flag must be cleared manually first. Same with SBC for subtract.
