Port over Bitmap 'radial_blur' from old SFML codebase

This implementation is also heaps better than the old
one as it doesn't use a (differently sized) aux texture,
meaning the Bitmap discards its old texture and aquires
one of same size, making reuse through the TexPool a
lot more likely. It also saves on the aux texture blits
and binding switches.

As the setup / resource acquisition far outweighs the
actual rendering cost, operation time is relatively
constant no matter how many divisions are used.

mkxp.pro

@@ -104,6 +104,7 @@ EMBED = shader/transSimple.frag \
         shader/simple.vert \
         shader/simpleColor.vert \
         shader/sprite.vert \
+        shader/simpleMatrix.vert \
         assets/liberation.ttf
 
 defineReplace(xxdOutput) {