OpenGL2: Small glsl shader optimizations, fixes, and cleanup.

code/renderergl2/glsl/bokeh_vp.glsl

@@ -1,4 +1,4 @@
-attribute vec4 attr_Position;
+attribute vec3 attr_Position;
 attribute vec4 attr_TexCoord0;
 
 uniform mat4   u_ModelViewProjectionMatrix;
@@ -8,6 +8,6 @@ varying vec2   var_TexCoords;
 
 void main()
 {
-	gl_Position = u_ModelViewProjectionMatrix * attr_Position;
+	gl_Position = u_ModelViewProjectionMatrix * vec4(attr_Position, 1.0);
 	var_TexCoords = attr_TexCoord0.st;
 }