First commit - work-in-progress and untested (but builds correctly)
DVBSub2 references and code deleted, unused TeletextPin.cpp and TeletextPin.h files deleted. Async logging updated.
Added fixes for Mantis 4252 (MP hangs at end of recording when skipping to end)
Fix for logging problem with Unicode strings
Remove unused teletextpin.h to fix build issue.
If file seeks get EOF, the roll-back time is now 0.5s when timeshifting, 3s for recordings (to minimise chance of seeking back to previous channel data and triggering OnNewChannel()
Merge branch 'FEAT-4339_Update_TsReader_to_v70_code'