Add support for HQx

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I've completed a shader implementation of HQx available here: 
https://github.com/Armada651/hqx-shader

I've not yet implemented a GLSL version, because the shader requires the 
following functionality:

* Passing additional textures to the shader.
* Applying multiply shaders to the output for better performance. (optional)

Could you add this functionality? I can provide a GLSL version if necessary, 
the shader code itself is pretty simple.

Attached you'll find a screenshot of the HQ4x shader running in RetroArch, 
they've included it in their common shaders repository.

Original issue reported on code.google.com by Jules.B...@gmail.com on 4 Jun 2014 at 9:27

Attachments:

• HQ4x.png

[GoogleCodeExporter]

Thanks. Will consider supporting multi-pass shaders.

Original comment by fastemul...@gmail.com on 5 Jun 2014 at 3:58

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[GoogleCodeExporter]

There is also a single-pass version in the "legacy" folder, you can implement 
it with just the additional texture support.

Original comment by Jules.B...@gmail.com on 5 Jun 2014 at 4:28

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