Drop pixman_blt calls

Currently we use pixman_blt to copy damaged region to shared outputs. Unfortunately pixman_blt is not guaranteed to be implemented and may return false. The caller is expected to implement a fallback in that case.

As discussed in !195 (closed) we should rather drop pixman_blt instead of implementing a fallback for it. This merge requests replaced pixman_blt with pixman_image_composite32. It replaced !195 (closed).