MFC r318514-r318515, r318517, r318917

r318514:
Use size_t.

Inspired by: OpenBSD src/lib/libc/stdlib/qsort.c,v 1.11

r318515:
The current qsort(3) implementation ignores the sizes of partitions, and
always perform recursion on the left partition, then use a tail call to
handle the right partition. In the worst case this could require O(N)
levels of recursions.

Reduce the possible recursion level to log2(N) by always recursing on the
smaller partition instead.

Obtained from: PostgreSQL 9d6077abf9d6efd992a59f05ef5aba981ea32096

r318517:
Sync qsort.c with userland r318515.

(Note that MIN macro is removed in favor of sys/param.h's version).

PR: 213922

r318917:
Disconnect heimdal version of qsort.c from build because we are already
using libc's version of qsort.

PR: bin/213922

MFC r311989 (cem):

libkern: Remove obsolete 'register' keyword

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

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

Copy qsort_r(3) from libc to libkern.

Reviewed by: phk
Approved by: julian (mentor)

Remove advertising clause from University of California Regent's
license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

Use __FBSDID().

Fix instances of macros with improperly parenthasized arguments.

Verified by: md5

Remove __P.

$Id$ -> $FreeBSD$

#include sys/libkern.h instead of stdlib.h.
PR: 7105
Reviewed by: phk
Submitted by: Robert Watson <robert+freebsd@cyrus.watson.org>

Support compiling with `gcc -ansi'.

Back out part 1 of the MCFH that changed $Id$ to $FreeBSD$. We are not
ready for it yet.

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.

Don't depend in the kernel on the gcc feature of doing arithmetic on
pointers of type `void *'. Warn about this in future.

Removed sccsids and rcsids and added Id$ to save space like everything
else in libkern.

Don't include <sys/types.h> when it isn't used.

This commit covers most of the ANSI library functions. Many others only
need <sys/types.h> because they use u_xxx.

Added prototypes.

Add qsort() to libkern, taken from libc.