MFC r312486:

Use SRCTOP-relative paths to other directories instead of .CURDIR-relative ones

This implifies pathing in make/displayed output

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.

Add an implementation of the RPCSEC_GSS authentication protocol for RPC. This
is based on an old implementation from the University of Michigan with lots of
changes and fixes by me and the addition of a Solaris-compatible API.

Sponsored by: Isilon Systems
Reviewed by: alfred