Fixed manual change for OGL renderer.

When I added manual change/erase, part of the implementation
was done in the software renderer... and it somehow broke
things for the OGL renderer...

This (should) fix the slowdown in Panzer Dragoon Zwei

git-svn-id: https://yabause.svn.sourceforge.net/svnroot/yabause/trunk@3054 d7be59e3-070e-4b9a-85a1-4646befae34d