OGL: Post-processing suite

It was requested by a few people, that I make a PR for this. It Includes;

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FXAA 3.11

Bilinear Filtering
Bicubic Interpolation Scaling
Lanzcos Interpolation Scaling

Blended Bloom /w 5 different bloom types.
Scene Tone mapping /w optional filmic operators
Colour Correction
Filmic Cross Processing
Gamma Correction Curve
Texture Unsharp Mask
Pixel Vibrance Adjustment
Local Contrast Enhancement
PX Cel Shading

Scan line Emulation
Film Grain
Vignette
Subpixel Dithering

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Each effect can be enabled, & disabled independently, and various options which can be configured via the post-processing GUI.