These are implemented as ScrollLock+Up/Down for volume up and down, and
ScrollLock+M to toggle audio mute. These should prove useful especially
when Looking Glass now supports streaming audio, and the volume is
defined in the guest and set on the output stream.
The cursorThread prevents the host from going to sleep when the
video feed is disabled as it's subscribed to the cursor queue. Stopping
the cursorThread will unsubscribe from the queue and allow the host
application to disable capture.
This adds a new `earlyInit` call which allows the overlay to register
options before actually being intialized. Also the keybind handling and
state tracking for each overlay has been moved internal to the overlay
itself.
Before, if you want to see the FPS, you need to close the client and
restart it with the -k switch to see the FPS. This is annoying.
This PR introduces a new keybind, ScrollLock+D, which, when pressed,
toggles the display of the FPS.
This is implemented for both EGL and OpenGL backends.
As the window manager may change our mode to full screen without our
request we must ask the ds backend for the current state when we want to
toggle the mode.
