vdagent: introduce VD_AGENT_CAP_CLIPBOARD_NO_RELEASE_ON_REGRAB

This capability means the peer will not send a release event between
two subsequent grabs. This helps with interaction issues with
clipboard managers which can be worked around by time-based filters at
this point. With this capability, there is no need for such filter.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Acked-by: Victor Toso <victortoso@redhat.com>

spice/vd_agent.h

@@ -303,6 +303,7 @@ enum {
     VD_AGENT_CAP_FILE_XFER_DISABLED,
     VD_AGENT_CAP_FILE_XFER_DETAILED_ERRORS,
     VD_AGENT_CAP_GRAPHICS_DEVICE_INFO,
+    VD_AGENT_CAP_CLIPBOARD_NO_RELEASE_ON_REGRAB,
     VD_AGENT_END_CAP,
 };