Allows the transfer of data according to the specs in dma.rs.

Also removed the not needed bitwise operation.

Avoids constant comparison against wx by cmputing the initial windows index.

By avoiding many of the GBC required operations in the drawing pipeline.

This is only a structure change and no real DMA implementation has been done.

Thsi avoids possible overflow issues.

The performance should be poor as there're lots of if clauses.

Including CGB and DMG.

This is a temporary hack until a real speed switch is available.

By computing only the color associated with the byte in question.
This avoid computation that was not required.