Fix libnsgif LWZ decoding buffer awfulness
Added incomplete handling of #include in shaders
Added partial handling of classes in shaders to ShaderProcessor
Added GPU based deinterlacing and refactored interlacing code

Added deinterlacing modes:
- Blend (GPU)
- Linear (GPU)
- Yadif (GPU)
each with source framerate and double source framerate mode.
Also added GPU based Retro deinterlacing
Fixed memory leak with deinterlacing in DeviceSource
Fixed an ancient memory leak in the DirectShow plugin