[Exim] Exim 4.12 RPM spec file

Hello all,

I've created a substantially new RPM spec file for Exim 4.12. Compared to
previous versions, it includes (optional) integrated support for:

- Eximon
- Exiscan
- SA-Exim

and simpler handling of custom Makefiles.

I believe everything's in order, but it hasn't been heavily tested, so any
feedback is welcome. You can download all you need at:

http://www.timj.co.uk/linux/exim.php


Tim