TCP send queue contains two types of data:
* unacknowledged data, which have been sent out
* data, which have not been sent

Currently only the size of all data is save, but it's not enough for
proper restoring of TCP connections.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>