Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

style.Makefile(5) police
(I've tried to keep to the spirit of the original formatting)

Reviewed by: des

Moved SHLIB_NAME definition into one place.

Approved by: des

Switch to OpenPAM. Bump library version. Modules are now versioned, so
applications linked with Linux-PAM will still work.
Remove pam_get_pass(); OpenPAM has pam_get_authtok().
Remove pam_prompt(); OpenPAM has pam_{,v}{error,info,prompt}().
Remove pam_set_item(3) man page as OpenPAM has its own.

Sponsored by: DARPA, NAI Labs

Clean up (and in some cases write) the PAM mudules, using
o The new options-processing API
o The new DEBUG-logging API

Add man(1) pages for ALL modules. MDOC-Police welcome
to check this.

Audit, clean up while I'm here.

Big module cleanup.

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).

Use a unified libgcc rather than a seperate one for threaded and
non-threaded programs. This provides threaded programs with the
needed exception frame symbols.

parts submitted by: Max Khon <fjoe@iclub.nsu.ru>
PR: 23252

Revive the pam_deny and pam_permit modules from Linux-PAM. They are
simple enough to be trusted.

Add account management functionality to the pam_unix module.

These changes should make it possible to use PAM in some ports.

Submitted by: Max Khon <fjoe@iclub.nsu.ru>