qxl: Add set_client_capabilities() interface to QXLInterface This new interface lets spice server inform the guest whether (a) a client is connected (b) what capabilities the client has There is a fixed number (464) of bits reserved for capabilities, and when the capabilities bits change, the QXL_INTERRUPT_CLIENT interrupt is generated. Signed-off-by: Soren Sandmann <ssp@redhat.com> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>