[turba] turba support for ACAP/IMSP

[Liam Hoekenga]

> Cyrusoft (http://www.cyrusoft.com), as part of their SilkyMail package
> (based on an _ancient_ version of IMP), has an imsp client library. I gave
> up long ago getting any kind of a response from them about releasing this as
> a genuine, standalone, open source library. If someone gets it released and
> available somewhere, I can dust off my php extension for it (from php3) and
> supporting it in Turba will be a snap.

I looked at the silkymail distribution of IMSP.  It's based on the IMSP code
from CMU, available at:

    ftp://ftp.andrew.cmu.edu/pub/cyrus-mail/imsp-api-v1.00a4.tar.gz

The version here wants to build itself into c-client.  The version that comes
with silkymail appears only to have enough of the c-client files needed to build 
"libimsp" (which judging by it's makefile, is simply a stripped down, renamed
libc-client.a).  The diff of the files they share (specifically imsp.c) are
minimal (specifically the changes in imsp.c).  It looks like there's one new
function in libimsp that isn't in imsp-api-v1.00a4 (imsp_abook_mfetch).  I'm
also guessing that libimsp does cleartext authentication, while the original CMU
version says it requires kerberos (which I'd love to have working, because we
already are using kerberized IMSP servers at umich).

At the very least, I don't see a problem going to CMU, downloading their source,
and doing what we need to do to it.

There's also this on freshmeat and sourceforge..

    http://sourceforge.net/projects/phpimspclass/

I'd kind of prefer getting the CMU stuff working tho (because it, at least
originally, did support kerberos for authentication).

Liam