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

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

Don't point users at the old csup homepage.

Approved by: lulf

- Move csup away from contrib/ and into usr.bin/. Software is no longer
contributed, and main development is happening in the FreeBSD repo.

Suggested by: joel

- Add support for CVSup authentication mechanisms to csup.
- Include a cpasswd script performing the same mechanisms as the cvpasswd
utility from CVSup.

PR: bin/114129
Submitted by: Petar Zhivkov Petrov <pesho.petrov -at- gmail.com>
MFC after: 1 month

This commit was generated by cvs2svn to compensate for changes in r156701,
which included commits to RCS files with non-trunk default branches.

Import the latest snapshot of csup (20060313).

Initial import of csup.