Remoting plugin for Weston

This patch series implements a remoting plugin that adds remote output support for the DRM backend.

A remote output is a virtual screen, not connected to any physical DRM device, that can stream its contents to a remote host. The current implementation uses GStreamer to create a MJPEG stream and transmits it over an RTP session.
The settings of the virtual output and the remote host are specified in weston.ini.

In the future, the aim is to also consider integrating ways to support input events from the remote host, so that a remote user can interact with the output.