r14325: Add pam_modules rule which builds the configure(d) pam modules. This is

r14325: Add pam_modules rule which builds the configure(d) pam modules.  This is
called as part of the all rule (again only if pam modules are requested
by configure).

Add pam_winbind rule.

Ensure proto_exists before we build the pam modules.

Add test_pam_modules rule to test if the built pam modules have any
unresolved symbols.  For test_pam_modules we use script/tests/dlopen.sh
which was written by Nalin Dahyabhai <nalin@redhat.com>.  Thanks Nalin!
RedHat and SuSE use this script to test nss and pam modules since
several years.
(This used to be commit 71b2eb55adcd28f3796254ea1ce0bcee6098e712)