* Move initial batch of shaders and presets to smoothing subdirectory
* Rename smoothing to edge enhancement
* Move cubic and windowed into interpolation
* Fix some presets
* Fix rest of presets
* Rename edge-enhancement to edge-smoothing
* Move pixel art scalers into separate directory separate from 'interpolation'
* Flatten interpolation/cubic into interpolation/
* make a bunch of implicit scaling rules explicit and move color shaders before scaling shaders in the handheld directory
* remove extraneous file
* switch vhs from viewport to source scaling
- Swap stock linear by cubic multipass shaders.
- Improves IQ for 4xSoft, 2xSaL, 2xSacaleHq, 4xScaleHq, HQ2x, HQ3x, HQ4x, 2xBRz, 2xSaI, Super-2xSaI and Advance2x-AA.
- Expose all the configuration settings used by the quality presets to allow fine-tuning of edge detection.
- Changed default edge detection technique from luma to color since in my tests that always yields better results.
- Increased quality to ultra in default preset.
- Deleted the duplication of the fragment shader part of the lib, as I figured out how to include the lib twice with different defines for the vertex and fragment passes. That is necessary probably because discard cannot be used in vertex shaders in RetroArch, indicated in a comment in the lib as a possible restriction in some compilers.
- Include license headers to make clear that all my contributions are released on the public domain under the terms of the Unlicense. Anyone can do whatever they want with this.
Adds a new port of SMAA. This includes the original sources unmodified. The original does a great job of ensuring compatibility with any shader compiler, so no need to modify it.
- Add a runtime toggle to choose edge detection technique;
- Position independent, doesn't need to be the first shader in a chain anymore.
