DIB Engine - Mostly fixed against test suite

[Massimo Del Fedele]

Remaining bugs are related to :

1) Some color on monochrome bitmaps.... here I guess nobody knows how to do it right. I fixed some todo wine (most) but have 2 failures which wine does right.
Seldom used anyways, and happens only on weird palettes. I guess not ever Microsoft knows what they did on this respect :-)

2) an AlphaBlend() call which should fail and doesn't. Here I really don't
know why it should fail..... Uninfluent, anyways.

3) GetDIBits on a source DIB with BPP <= 8 fails to retrieve the original DIB palette, and synthesizes a new one instead.
For the moment I found no simple way to grab the palette from inside GetDIBits without maintaining a linked list
of HBITMAP <--> internal bitmaps. Not worth the effort for the moment anyways.
If somebody notices weird colors due to it, I'll try to fix.....

There are still some missing/buggy features rarely used that aren't spotted by testsuite;
by now I've no time to fix them, anyways no one felt into them up to now :-)

Austin, could you please retest it against test suite ?

(code on Bug421 page)

Ciao

Max