Fix crashes when the master clock goes faster than 60 Hz.

This could happen in particularly when using a video as the master card;
e.g. Larix Broadcaster sometimes sends SRT with 60.06 fps or similar.
We solve it by completely rewriting how DTS is calculated when doing
Quick Sync encoding, which ended up being much simpler than what we
had before (and probably a lot more common)

This essentially removes the meaning of MAX_FPS; we could now easily
do e.g. 144 fps if needed.