add some X error handlers handling magic
render to GLXPixmap in render queue to workaround hanging on dri throttling

current version of flash player often destroys Drawable before presentation
queue which draws window away from GL context while it's painting. With
dri throttling on Xorg side that can lead to dropped response. That in
turn makes mesa hang somewhere inside ordinary call. Rendering to GLXPixmap
and then copying it to Drawable looks like acceptable solution.