Remove darwin/llvm workaround forcing to build with -O3.

Seems to work fine now, and it makes debugging more difficult
Update myth mpeg-ts probing score calculation to match FFmpeg's own.

the mpegts probe used to be identical, but has been changed over time, always related to bug fixes.
This will allow to differentiate more easily between the two demuxers
mpegts: check substreams before discarding

Allow to extract the AC3 core from TrueHD with the "copy" codec.

From FFmpeg's 07584eaf4a95db3f11d3bc411f9786932829e82b commit
mpegts: fix handling of files smaller than 8kb

Fixes FFMpeg Ticket1094

From FFmpeg's commit 04064e1c200832c344b97307e24c30653d9835ce
mpegts: Fix potential memory leak in mpegts_read_packet()

This leak can happen in case of some error paths.

From FFmpeg's commit 5710dbf88cd56e7fbee7ad70240f92fe82ce6566
mpegts: Make sure we don't return uninitialized packets

This fixes crashes, where the demuxer could return 0 even if the returned AVPacket isn't initialized at all. This could happen if running into EOF or running out of probesize with non-seekable sources.

From FFmpeg commit df8aa4598c7cc1c2f863f6fc6b2d4b3e6dc7345e
Re-enable FFMpeg's original mpegts demuxer

MythTV's one will always be selected when performing a media probe.
Should MythTV's own mpegts demuxer fail to open the file, try using FFMpeg's original one

It's no nice fix and we should really fix it in our own's demuxer; however decision has been made to port our changes upward and start working on using FFmpeg's one

Fixes #11692
Fix compilation warning about unused method on mac
Add setting to always use FFmpeg's MPEG-TS demuxer when available.

This will be used for debugging while transitioning to this demuxer
Add #define to determine if myth was compiled in debug or profiling mode
Add GUI to force the use of FFmpeg's own MPEG-TS demuxer.

Option will only show on debug build