Enable threaded_video, change default shaders...

...let shader preset decide if bilinear filtering (video_smooth) is necessary.

And please add the newer brighter phosphor.glslp:
http://blog.petrockblock.com/forums/topic/video-filters-scanlinesntsc/#post-4996
Merge pull request #269 from gizmo98/patch-2

Enable threaded_video, change default shaders...