[cvsnt] Latest updates

[Tony Hoyle]

cvsnt 2.0.16

Another load to test over the holidays...  ready for 2.0.17 to (hopefully)
be stable for January.

* First implementation of binary diff.  This is just a proof of concept at
the moment - you can put files in, and (probably) get them out intact again
later. 
  - To make a file using binary diff you must 'add -kB' a new file.
  - It is not currently possible to use admin -kB to change the file
    type and get anything like sane results.  You cannot therefore change
    an existing file to use binary diffs.
  - I haven't really tested it that hard, just added a few revisions and
    retrieved them.  Branch merging, etc. is untested.

* Reinstate lost PAM support into Unix version (service name is 'cvs').

* 'update -3' 3-way diff, for frontends to process.

* Local mode unicode works now.

Tony