Bug #1101: Fix PaintWindow in the pixmap case when the window's origin is
not at the backing pixmap's origin. Resulted in incorrect rendering in at least aisleriot, fluxbox, and KDE apps, and probably many more. While here, move the ParentRelative loop above the drawable grab -- may improve correctness with ParentRelative background origins as well. Note that the border code doesn't handle ParentRelative yet.