migration_protocol: add inputs channel migration data
migration_protocol: add inputs channel migration data

Storing the motion count in uint16_t and not in uint32_t since
the exact count is not important, just its division in
SPICE_INPUT_MOTION_ACK_BUNCH (see the next 2 patches).

mathslinux/spice,alon/spice-server,Fantu/spice,fgouget/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,mathslinux/spice,freedesktop-unofficial-mirror/spice__spice,Fantu/spice,alon/spice-server,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,fgouget/spice,elmarco/spice,alon/spice-server,ya-mouse/spice,Fantu/spice,freedesktop-unofficial-mirror/spice__spice,fgouget/spice,mathslinux/spice,Fantu/spice,alon/spice-server,ya-mouse/spice,elmarco/spice,elmarco/spice,fgouget/spice,alon/spice-server,elmarco/spice,mathslinux/spice,ya-mouse/spice,mathslinux/spice,freedesktop-unofficial-mirror/spice__spice,SPICE/spice,elmarco/spice