Tl sync

Dear Martin,

This PR is about 2 situations that I encountered with Joker synchronisation. First I have noticed frequent jumps of one or two frames with both LTC and MTC, that are solved by increasing the tolerance from 1000 ticks to 2000. Then I have noticed semi-random jumps when controlling Joker from MidiTool. These jumps were caused by PhTime being changed in the middle of a quarter-frame sequence of messages. The two commits of this PR fix these issues.

Thanks again for Joker !!

Best regards,

Timothée