Deoldify Vapoursynth filter

[zspeciman]

Dan, your colorization job of Young Frankenstein is outstanding.  Those other two pale in comparison.  The stubborn red flickering are either nonexistent or not distracting.  This is the most significant update you've made.
I'm curious if you tested the stability with movies that have hardcoded subtitles, especially in dark scenes.  If the sudden appearance and disappearance of those bright white letters have any impact.