Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Merge nc(1) from OpenBSD 4.4. While there, rename our '-O' (no
tcp options) to '--no-tcpopt' in order to resolve a comflicit
with OpenBSD's -O semantics.

This commit was generated by cvs2svn to compensate for changes in r178382,
which included commits to RCS files with non-trunk default branches.

Import netcat as of today's OPENBSD_4_3 snapshot.

Import netcat from OpenBSD 3.9-RELEASE.