There are different namespaces for control and transport service

Manually merged upstream commit b59259c9937938bdbeb1b802a4481ef33c792690,
I am at a point where automatic merge would not work
Qualify namespace choices

Manually merged upstream commit fd8f9c7f1a451c2996e01b327e402f40097004a3
Include 'channel' attribute in volume-related event variables

Manually merged upstream commit 238a3c64f74bbad4668bdc3282a38f934d707444
Add 'Loudness' to the set of attributes that need 'channel' qualifier

Manually merged upstream commit 90f9b9b4fdcf2071fa611ee6d356601500b03710
ignore non-eventable variable when building LastChange

When using LastChange, not all modified variables must be sent in event.
We use sendevents flag to filter out unwanted variables.
See:
    https://github.com/hzeller/gmrender-resurrect/commit/47da829144e540a2d944ee976500c13a97fdb9b8
	https://github.com/hzeller/gmrender-resurrect/commit/ed0f527763a0e81fcc9ccb0e8aa4306ed6d082d5
do not send non-evened variables on initial sync

See:
    https://github.com/hzeller/gmrender-resurrect/commit/47da829144e540a2d944ee976500c13a97fdb9b8
    https://github.com/hzeller/gmrender-resurrect/commit/ed0f527763a0e81fcc9ccb0e8aa4306ed6d082d5
clean up evented variables