That looks good, thanks! I'll try to get it included and set as default.
If you're going to add this to the build, make sure it's diasabled by default.
The shader source looks good to me, but it really needs a lot of testing to run on "most" hardware. There are tonnes of compatibility issues experienced with shaders developed on one card, tested out on another. AMD Cards often need extra attention and are less forgiving.
Also, think of the machines without shader support at all. :-(
On the actual shader; I think it looks great. Like HQ2X or such.