VLCTime: add clock and delay from LibVLC

[VLCTime clock] will match libvlc_clock() and [VLCTime delay:ts] will match libvlc_delay(ts).

They are returning and taking int64_t as parameter, much like libvlc itself, so as to avoid allocation of the VLCTime wrapper.

changed milestone to %4.0

added Feature label

assigned to @alexandre-janniaux

marked this merge request as ready

Are you sure libvlc_delay is part of the LibVLC public API?

resolved all threads

merged