Move common stuff into Makefile.inc, and tidy up all the Makefiles
as a result.
Build new modules.
Put a commented-out dependancy on libpam for the (shared) modules.
I can't bring this in just yet, as the dependancy (modules->libpam)
is reversed for the static case (libpam->modules).
pam_krb5 is a Kerberos 5 (Heimdal) authentication module.
pam_nologin checks for /etc/nologin and does the "usual stuff"
if it is found, otherwise it silently succeeds.
pam_rootok silently succeeds if the user is root, otherwise
it fails.
pam_wheel silently succeeds if the user is a member of group
"wheel" (or another nominated group), and fails
otherwise.
There is an issue with kerberosIV and kerberos5 - if both are
being built, then static linking fails with duplicate symbols.
This will take a bit of work to sort out in the kerberii.
