* Avoid clearning alpha channel by handle when presenting
Previous code was binding then blitting while the framebuffer was bound
and then clearing the alpha channel by its handle.
This ended up triggering a bug since AMD driver 21.4.1 ending up
clearing the whole framebuffer as a result.
New code fix this weird logic by applying the clear on the bound
framebuffer.
Close#2236.
* Address rip's comments
* Fix AMD being broken once again