Deprecate `ld [c], a` and `ld a, [c]`

[Rangi42]

ldh [c], a and ldh a, [c] are preferred.

The opcode table should also be updated.

[nummacway]

Don't know if this needs its own issue, but documentation for one command uses an uppercase and the other a lowercase C to refer to the address ($FF00+C vs. $FF00+c). This should be made consistent. One might even want to spell this out, because this is the only case of C having a special purpose:

Copy the value in register A into the byte at address $FF00+C ($FF00 plus the unsigned value in register C).