we now have 'virtual' video support. Every video front-end defines a
static, initialized structure 'Video_xxx' (e.g. Video_console)
which contains (mostly) pointers to the appropriate routines
for certain tasks.
Please use this when implementing new video front ends!
(See video/video.h for more info)
most of the video code & defs is removed from emu.c and emu.h
(now mostly in video/video.c)
int10.h no longer exists (now in video/int10.c)
sigalrm now again checks the dirty bit(s) in vm86s.screen_bitmap
before calling update_screen.
At the moment, it doesn't seem to achieve much, but it might help
when we use mark's scroll detector, and will be absolutely necessary
for a good X graphics support.
Note that for all video memory modifications done outside of vm86
mode we must now use set_dirty() (defined in int10.c).
this is currently disabled. To enable it, set VIDEO_CHECK_DIRTY
to 1 in include/video.c.