Add cfchecker, cdat-lite, and udunits.

> This is through a proxy, so it might be a configuration issue on my end...

Nope ... Unidata have deleted the file and replaced it with 2.2.16. :disappointed:

Since they don't seem to provide persistent downloads (:disappointed:) we *could* indirect the link via the [versions](ftp://ftp.unidata.ucar.edu/pub/udunits/versions) file they provide. Yeuch. :disappointed: