Fix -N flag to actually shut down the (entire) socket when the input
goes away. This allows for using nc in cases where the network server
will no longer expect anything after eof, instead of hanging waiting
for more input from our end.
Additionaly, shut down if tls is in use if either side of the socket
goes away, since we higher level TLS operations (tls_read and write)
will require the socket to be both readable and writable as we can
get TLS_WANT_POLLIN or TLS_WANT_POLLOUT on either operation.
deraadt@ buying it. found by sthen@
UnifiedSplitRaw
