Fixes screen not updating or getting updated inconsistently when apps blit to 
front buffer or lock it when RenderTargetLockMode=readtex, as happens in e.g. 
Red Alert 2 and also in p8_primary_test in ddraw tests.

server: When moving/resizing a window crop the update region against the new rectangle of the parents.

Based on a patch by Olivier Samyn.

Fixes a failure in p8_primary_test when running with opengl ddraw renderer.

Fixes failure in p8_primary_test when using opengl ddraw renderer.