Multimedia keys API regression in gnome-settings-daemon 3.24

[Bastien Nocera <hadess hadess net>]

Hey,

After splitting up gnome-settings-daemon in small independent daemons
for the GNOME 3.24 release, making it more robust and easier to debug,
a regression was discovered in gnome-settings-daemon's multimedia keys
plugin, which handles, well, multimedia keys and offers up an API for
applications.

For around 6 years, the API implemented by the multimedia keys plugin
did not match the API documentation for it. A work-around was put in
place for GNOME 3.24, and a fix for both development and older versions
is available to make the implemented API match the documented one.

Forward compatibility for GNOME 3.22:
https://git.gnome.org/browse/gnome-settings-daemon/commit/?h=gnome-3-22&id=12c92274bc118836d9c6dcb5262b82536ef2fe58

Work-around for GNOME 3.24:
https://git.gnome.org/browse/gnome-settings-daemon/commit/?h=gnome-3-24&id=42f75ed4cdc86498d6e02e511a1314b8916bd4aa

Fix for GNOME 3.26:
https://git.gnome.org/browse/gnome-settings-daemon/commit/?id=33d47e655606ac88ed7d529c1132e5be6299633b

The downside of this is that applications will need to be modified to
use the D-Bus name as documented since 2011, rather than the cargo-
culted D-Bus name that was used.

The patches are small enough but they will be numerous.

Examples for totem:
https://bugzilla.gnome.org/show_bug.cgi?id=781589
and rhythmbox:
https://bugzilla.gnome.org/show_bug.cgi?id=781664

Cheers