Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

- 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

Merge support for CVSMode (aka. mirror mode) into csup. This means csup can now
fetch a complete CVS repository. Support for rsync update of regular files are
also included, but are not yet enabled. The change should not have an impact on
existing csup usage, as little of the existing code has changed.

- Import csup work from p4.