sock_sendmsg() modifies iovec passed to it - it sets all length members of
iovec array to zero on success transmission (and even on failed if it
fails after iovec copy, but...) and advances pointers to point at the end
of buffers used. This has an unfortunate effect that ncpfs's retry on
failure does not work for IPX/UDP connections - kernel refused to do anything
because length from iovec was 0 while length passed to sock_sendmsg() was
correct.

This simple fix gets rid of a problem by creating temporary iovec copy, which can
sock_sendmsg destroy if it has such wish.