[Exim] Still having trouble with PAM

I'm still having trouble with PAM support. My understanding is that
this will allow me to use alternate authentication methods built into
OS X. I have not used PAM before on Linux either, so my understanding
of PAM and how it works is pretty basic.

Anyway, at this point I haven't been able to get it to compile yet. Can
someone explain how the compiling procedure for PAM in Exim works even
on a different platform? Is it possible to point the compiler to the
shared libs already on the system, or does it have to have the original
PAM source files? Once I get it compiled, are there any caveats to
using it? I am hoping that I can get rid of the hand edited text file I
currently have and be able to manage my users in one place.

If there is an easier method to accomplish this goal if someone would
lend me a hand or point me in the right direction, that would be
greatly appreciated.

Thanks,
Kevin