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.

src/shader.h

@@ -118,6 +118,17 @@ private:
 	GLint u_spriteMat;
 };
 
+class SimpleMatrixShader : public ShaderBase
+{
+public:
+	SimpleMatrixShader();
+
+	void setMatrix(const float value[16]);
+
+private:
+	GLint u_matrix;
+};
+
 class TransShader : public ShaderBase
 {
 public: