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

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

Build lib/ with WARNS=6 by default.

Similar to libexec/, do the same with lib/. Make WARNS=6 the norm and
lower it when needed.

I'm setting WARNS?=0 for secure/. It seems secure/ includes the
Makefile.inc provided by lib/. I'm not going to touch that directory.
Most of the code there is contributed anyway.

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

Reviewed by: des

Just to show that PAM can do almost anything from the ridiculous to the
obscene, or - as they say in New York - sophisticated, add pam_echo(8) and
pam_exec(8) to our ever-lengthening roster of PAM modules.

Sponsored by: DARPA, NAI Labs.