Fix typo.

Found by cppcheck
Setting VERSION to v0.27-alpha
Reverting version change due tu a permission problem
Make translatable strings extractable and change context.
Remove redundant QObject::, the class already inherit tr() from
QObject
Make sure any stored packets are flushed when the DVDRingBuffer needs to wait for the player.

This fixes playback issues with still frames when using VDPAU (or when the 'Extra audio buffering' option is enabled) due to the still frame getting stuck in the decoder's buffers and the player running out of frames.
Fixed flickering playback when transistioning from/to a still frame with OpenGL playback.  The underlying issue (paused video not being unpaused) occured with VDPAU playback too but did not seem to cause any visible issues.
Remove some QObjectt:: and replace them with a local class
Ensure cancelling a download is done in the same thread it started

This prevent Qt to crash with "Cannot send events to objects owned by a different thread."

Fixes #11663
Setting VERSION to v0.27-alpha
Rename MythUINotificationCenter into MythNotificationCenter

This is to make naming consisten with other myth libraries, and using MythUI prefix only for MythUI widgets.
Make distclean required
Make mythnotificationcenter.h included in mythmainwindow.h

Make consistent use of GetNotificationCenter() across the board as this is the official way of getting the Notification Center instance. This allows to remove the need to include mythnotificationcenter.h in most cases.
Way too many includes already...
Bump API version following rename of MythUINotificationCenter
Lock the various stream context to prevent racing conditions.

SeekReset was called in player thread, which would reset the av streams, while sometimes in the middle of usage in the decoder thread.

Fixes #11705
Merge branch 'master' of code.mythtv.org:mythtv
Add extra logging to AvFormatDecoder::ReadPacket to log unexpected events from DVDRingBuffer that trigger a retry.
Query DVDRingBuffer's state directly from AvFormatDecoderDVD rather than relying on errno being passed back through ffmpeg code untouched.  This was sometimes preventing a (required) retry from occuring and breaking playback.
Make it possible to clear DVD bookmarks again.
Fixes Visual Studio compilation
Update ABI version

Probably not necessary, but just in case