Implement Bitmap 'blur'

I was a bit confused at first because I thought Enterbrain
had actually implemented a full Gaussian blur, but nope,
just dumb averaging.

shader/blur.frag

@@ -0,0 +1,16 @@
+
+uniform sampler2D texture;
+
+varying vec2 v_texCoord;
+varying vec2 v_blurCoord[2];
+
+void main()
+{
+	vec4 frag = vec4(0, 0, 0, 0);
+
+	frag += texture2D(texture, v_texCoord);
+	frag += texture2D(texture, v_blurCoord[0]);
+	frag += texture2D(texture, v_blurCoord[1]);
+
+	gl_FragColor = frag / 3.0;
+}