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

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

Fix conditional expression: previously a bitvector would be operated
on by a logical not.

Approved by: cperciva
MFC after: 3 days

- 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.

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.