[server] BufferInterface can resolve size through egl extension
Uses eglQueryWaylandBufferWL (if available) to determine the size of the buffer. In order to do so, the server library links against egl (1) and one needs to register the EGLDisplay in Server::Display by the user of the library. For this a new method Display::setEglDisplay is added. 1: not using epoxy as it doesn't wrap the Wayland interfaces yet.