[Exim] Exim Sieve filter

Hello,

a while ago I talked about implementing Sieve for Exim. By now I have
alpha code working as a patch relative to Exim 4.15. This is intended
for development and people who like the bleeding edge, not for production:

http://www.moria.de/~michael/sieve/

Feedback is very appreciated, in case anybody tries it.

Michael