Drawing the bottom-left start center image had multiple errors.
New images didn't set the default clip rect and weren't correctly
resized. The damage handling was also missing for alpha bitmaps.

Change-Id: Idabacbb8b507c990a24006152f064ae4f144b89e
Reviewed-on: https://gerrit.libreoffice.org/47277Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>