videomode: port from NetBSD to Minix.

 - Use standard headers instead of NetBSD kernel headers.
 - Define macros for missing functions aprint_debug, abs.
 - Other minor fixes to get edid.c, pickmode.c, vesagtf.c to
   compile and link with the Minix frame buffer driver.

Change-Id: I9ee523afed0c404dc0d745dab042cc0feb223875
fb: snapshot of work-in-progress

Change-Id: I08e6587b4182e2789648d8d04aeef44a7d3e6a04