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.

shader/simpleMatrix.vert

@@ -0,0 +1,20 @@
+
+uniform mat4 projMat;
+uniform mat4 matrix;
+
+uniform vec2 texSizeInv;
+
+attribute vec2 position;
+attribute vec2 texCoord;
+attribute vec4 color;
+
+varying vec2 v_texCoord;
+varying vec4 v_color;
+
+void main()
+{
+	gl_Position = projMat * matrix * vec4(position, 0, 1);
+
+	v_texCoord = texCoord * texSizeInv;
+	v_color = color;
+}