remove hardwired path. add support to override SYSINC and SYSLIB location from external buildscripts

This value seems to work unreliably and, according to a reliable source, it should be fine to just ignore it.

Also requires the WIP changes from the branch over at firmware.

Also remove a few lines of unused code and don't send src_pitch, since it's always 16 pixels for BlitPattern.

With a 32x48 mouse cursor image, the dummy/mask line is eight bytes instead of four.

Reuses the register for sprite_bitmap, since these operations are intertwined enough.

Merge branch 'rtg-driver-update-2' of https://source.mntmn.com/MNT/zz9000-drivers into rtg-driver-update-2

This saves some processing time on the Amiga side a bunch of the blitter ops data sent to the card.

Namely InvertRect, Planar2Chunky and RectFillNoMaskComplete