Add primary support for LUNA-88K 4bpp/8bpp frame buffer.

Add primary support for LUNA-88K 4bpp/8bpp frame buffer.

This brings color support on LUNA's wscons.  And, with the help of recent
development version of 'mlterm-fb' (frame buffer version of ports/x11/mlterm),
graphic images can be displayed in 16/256 colors on the screen.  Thanks to
arakiken, the original developer of mlterm!

This diff is based on NetBSD/luna68k work:
http://mail-index.netbsd.org/source-changes/2013/12/28/msg050266.html

Need more work to coexist with the monochrome X.Org server.

"go ahead!" miod@