[AD] [WIN] page flipping fix for the overlay driver

[Eric B. <ebo...@li...>]

This is the final patch (I hope !) in the long saga of the DirectDraw page
flipping code. It mainly fixes the flicker problem of both page flipping and
triple buffering for the overlay driver: exupdate 2 & 3 should now
flawlessly work.

The other things:
- moves the driver-specific init/exit code from wddbmp.c and wddraw.c into
wddovl.c,
- adds hardware color conversion (rather sexy feature: 16<-->32-bit
conversion at no cost; but it can't deal with 8-bit color and, on my ATI
card, all the hardware-accelerated primitives must be disabled),
- handles hardware limitations on the size and position of the displayed
overlay surfaces (but I can't test the code since my card seems to have no
such limitations...)

For me, the DirectDraw subsystem has no more visible bug; but, as it was
originally centered on the fullscreen driver, the two windowed drivers don't
fit very well into it and this ends up with many hooks and a significant
amount of duplicated code. So some cleanup work should be done (after a
release validating the present code...)

--
Eric Botcazou (ebo...@mu...)
Web Site: http://www.multimania.com/ebotcazou