gdebugcontroller: Add debug controller API and D-Bus implementation
This is intended to provide a uniform interface for controlling whether the debug output from an application (or service) is emitted, typically to journald, but actually to wherever the application chooses to output it.
The main implementation of GDebugController is GDebugControllerDBus,
which is intended to be used on Linux. Other implementations may be
added in future for other platforms, or larger applications may want to
provide their own implementation which integrates with their ecosystem.
The GDebugControllerDBus implementation exposes a D-Bus interface at
/org/freedesktop/Debugging with a method to enable or disable debug
output at runtime.
This could be used by external harnesses, such as GNOME Builder or systemd, to give a uniform way to get debug output from an application.
Signed-off-by: Philip Withnall pwithnall@endlessos.org
Fixes: #1190
Closes #1190