Make default duration of error 10s

5s could make it a bit hard to read
Exit early if playback didn't start due to an error.

Even if playback failed to start following an error, it would try to play regardless, waiting for playback to actually start, and aborting 20s later.

Required for #11656
Display error as to why playback failed to start.

Playback would otherwise fail silently, with the user wondering why.

Fixes #11656
Fix compilation warning.

warning: adding 'uint' (aka 'unsigned int') to a string does not append to the string
Use QMutexLocker to lock BonjourRegister

Following 29fae07f, use a QMutexLocker instead.
Rename static class member to follow MythTV coding style
Use notifications instead of popup in recording screens to indicates the availability of a recording
Do not display backend is online notification again after it's already been displayed earlier
Create AirPlay server after MainWindow got initialized.

Got an instance where AirPlay got ready before the main window was up and attempted playback causing a crash
Add methods to query state of modifications and remove notification from screen

Will be used with OSD and fixing #11657
Allow dismissing notification during video playback

Fixes #11657
libva (VAAPI) has changed their API. Use the legacy API.

Validated as working by Frank P.

Fixes #11631

Signed-off-by: Gary Buhrmaster <gary.buhrmaster@gmail.com>
Signed-off-by: Jean-Yves Avenard <jyavenard@mythtv.org>