Temporarily default Wayland and Mir to disabled, for 2.0.2 release. We'll flip the default back to enabled right after 2.0.2 is finalized, and try to declare them stable and ready by 2.0.3. Those that have an interest in supporting them in 2.0.2 can manually enable them in the configure script with --enable-video-wayland and/or --enable-video-mir.