comms/kermit: update C-Kermit to the latest version 10.0 Beta.06

Starting with Beta.05, distfiles are named cku400.*, not cku10.0.* as
they have been since 10.0 Beta.01, for conformity with all previous
releases when they were cku300, cku301, cku302, etc. Hardcode "400"
for the moment; it could be "401" or any higher number as development
progresses, but exact version mapping scheme is currently unclear.

Nudged by: ler