[PATCH] Fix of "IntGdiCombineRgn requires hSrc2 != NULL" bug

Created an attachment (id=5829)
Patch fixing all described bugs

It fixes using of NULL regions in IntGdiCombineRgn calls.
Removed unnecessary and ugly hack in DrawMenu. This code works well without hack.
As a bonus fix for UserRedrawDesktop, which fixes some glitches after changing display mode. I have no idea why there was used hrgnUpdate. It worked because this handle was NULL in majority of cases. Now it always repaints whole screen as it should