GL_INDEX is definitly not the way to load U8V8 surfaces

gdi32: Revert 1440eb5a and add the test showing that the change was wrong.

Prevents a crash when selecting text outside of a richedit control box.

Fix the case where the scrolling amount exceeds the window but still
falls within the clipping rect. This generates an additional update
region that needs to be invalidated.

Based on a patch by Lei Zhang.