[cvsnt] Latest updates

[Tony Hoyle]

cvsnt 2.0.51b

* Some extra security features for Unix (chroot & run as unprivileged user).
* Fix for multiple imports
* Upgraded putty client to 0.55 (security update)

Most users probably don't need this release so no need to upgrade if 
you're not seeing the import problem.  However, if you're using :ssh: 
then upgrading the clients is recommended for security reasons.

Tony