Add rendernode support to headless-GL backend
Submitted by Pekka Paalanen
Assigned to Wayland bug list
When supported by Mesa, let the headless backend with GL-renderer run on real hardware by using rendernodes underneath. Choose this mode with renderer=rendernode-gl.
The major point of this addition is to enable EGL_WL_bind_wayland_display support, and allow running hardware accelerated Wayland clients.
Add a test, where a hardware accelerated GLESv2 client draws a simple picture, sends it to the compositor, and waits for frame callback.