add stream report messages

If the server & client support SPICE_DISPLAY_CAP_STREAM_REPORT,
the server first sends SPICE_MSG_DISPLAY_STREAM_ACTIVATE_REPORT. Then,
the client periodically sends SPICE_MSGC_DISPLAY_STREAM_REPORT
messages that supply the server details about the current quality of
the video streaming on the client side. The server analyses the
report and adjust the stream parameters accordingly.
add SPICE_MSG_PLAYBACK_LATENCY

SPICE_MSG_PLAYBACK_LATENCY is intended for adjusting the
latency of the audio playback. It is used for synchronizing
the audio and video playback.
The corresponding capability is SPICE_PLAYBACK_CAP_LATENCY.