virtio-gpu: Improve virgl support.
virtio-gpu: Improve virgl support.

A slot, virgl-data, is added to the virtio-gpu structure to allow virgl
to store more complicated data.
Support for the resource-unref operation is added.
virgio-gpu-ctx-create is modified to properly support the debug name.

froggey/Mezzano,froggey/Mezzano