Acceleration of 2D operations for kdrive

[Alan]

> We also do blits (graticules, waveform masks),  rectangle fills (meters 
> and bar graphs).
> 
> Just because YOU don't need these things does not mean they are not needed.

This works both ways. Just because you need it I don't have to write it.

kdrive should actually accelerate horizontal/vertical lines as rectangles
but if you want arbitary line acceleration and need kdrive support for it
and your hardware you'll need to do a little coding.

Alan