[python] fix null pointer dereference when invoking non-addon scripts
AppMessenger: support for setting volume
AESinkPUSLSE: Use ApplicationMessenger to alter internal volume
AEStreamInfo: Handle sync headers with extension blocks

Fixes passthrough of Dolby TrueHD audio with Atmos.

Behavior based on FFmpeg patch "mlpdec: support major sync headers with
optional extension blocks" by Hendrik Leppkes.
FFmpeg: Temporarily dolby atmos fixed version (n2.4.1)
Language and Settings: Rename normalizevolumes to maintainoriginalvolume
ActiveAE: Maintain original volume is the inverse of normalizelevels
Maintain original volume: Move it to expert settings and enable it by default
VAAPI: Name driver that we don't like when closing the decoder