More implementation.  Passes tests 4, 5, 6, 7.  9 is broken, reportedly on XOR, but I suspect the problem is elsewhere.

add: SUB, SBC, LD, JP, RST, SWAP, RETI
fix: another JR negative displacement bug :/
More implementation, now passes test 1.

add: CP, DAA (adapted from DKParrot's emulator, linked in source), CPL
fix: lower four bits of F are always zero