Possible size optimization.

[mbaze]

Hi Einar,

it looks to me that you could save two inc cs in your dzx0_standard_back.asm decompressor. However, it would necessitate inverting the flags. This way add a,a which happens after every lddr would set carry to 1. Subsequently, instead of calling dzx0sb_elias it would be enough to call the opcodes just above, that is rl c + rl b which conveniently sets BC to 1. I think similar optimization could be made also in the forward compressor which I didn't look at yet.