wayland: remove stub for unimplemented function
osc: keep track of the "fullscreen" state when it changes

This avoids having to poll the "fullscreen" property in the tick
callback.
command: format_bitrate: fix conversion to kbits and mbits

Bitrates are now expressed in bits/second. This commit fixes conversions
which assumed it was still in bytes/second.

Signed-off-by: wm4 <wm4@nowhere>