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

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

Build usr.bin/ with WARNS=6 by default.

Also add some missing $FreeBSD$ to keep svn happy.

Add the ability to clean up all shared memory segments which are
unused in one go.

From the original PR:

I've observed that linux apps running under the linuxulator
have a habit of leaving behind shared memory segments which
are unused, but which eventually cause the system to run
out of free segments and these apps will stop working.
ipcrm(1) currently only allows removal of unused message
queues, shared memory segments and semaphores on an individual
basis, or those having a matching (non-zero) key. However
it would often be convenient to just do a complete cleanup
of everything, usually as root.

PR: bin/118292
Submitted by: Callum Gibson <callumgibson@optusnet.com.au>
Not reviewed by: grog@
Approved by: grog@

Fixed style of DPADD and LDADD assignments as per style.Makefile(5).

Don't install setgid kmem.

$Id$ -> $FreeBSD$

Revert $FreeBSD$ to $Id$

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

Imported the NetBSD version which acts a lot more like the SYSV program.

Obtained from: NetBSD

Added from FreeBSD-1.1.5 with some additions to list shared memory segments.