'RELENG_6_0_0_RELEASE'.

This commit was manufactured to restore the state of the 6.0-RELEASE image.

whose version has not already been bumped since RELENG_5 are being
bumped.

Revisions of files being MFC-ed:

> Path						Revision
> src/gnu/lib/libdialog/Makefile		1.43
> src/gnu/lib/libg2c/Makefile			1.16
> src/gnu/lib/libobjc/Makefile			1.27
> src/gnu/lib/libreadline/Makefile.inc		1.12
> src/gnu/lib/libregex/Makefile			1.32
> src/gnu/lib/libstdc++/Makefile		1.56
> src/kerberos5/lib/Makefile.inc		1.7
> src/lib/Makefile.inc				1.3
> src/lib/libalias/Makefile			1.31
> src/lib/libarchive/Makefile			1.37
> src/lib/libbegemot/Makefile			1.3
> src/lib/libbluetooth/Makefile			1.2
> src/lib/libbsnmp/Makefile.inc			1.6
> src/lib/libbz2/Makefile			1.6
> src/lib/libc_r/Makefile			1.42
> src/lib/libcrypt/Makefile			1.36
> src/lib/libdevstat/Makefile			1.15
> src/lib/libdevstat/devstat.h			1.11
> src/lib/libedit/Makefile			1.29
> src/lib/libexpat/Makefile			1.5
> src/lib/libfetch/Makefile			1.45
> src/lib/libftpio/Makefile			1.14
> src/lib/libgpib/Makefile			1.2
> src/lib/libipsec/Makefile			1.17
> src/lib/libkiconv/Makefile			1.3
> src/lib/libmagic/Makefile			1.7
> src/lib/libmp/Makefile			1.10
> src/lib/libncp/Makefile			1.6
> src/lib/libncurses/Makefile			1.79
> src/lib/libnetgraph/Makefile			1.11
> src/lib/libngatm/Makefile			1.6
> src/lib/libopie/Makefile			1.21
> src/lib/libpam/Makefile.inc			1.17
> src/lib/libpthread/Makefile			1.54
> src/lib/libradius/Makefile			1.12
> src/lib/libsdp/Makefile			1.4
> src/lib/libsmb/Makefile			1.8
> src/lib/libtacplus/Makefile			1.7
> src/lib/libthr/Makefile			1.14
> src/lib/libthread_db/Makefile			1.6
> src/lib/libugidfw/Makefile			1.7
> src/lib/libusbhid/Makefile			1.10
> src/lib/libutil/Makefile			1.57
> src/lib/libvgl/Makefile			1.11
> src/lib/libwrap/Makefile			1.17
> src/lib/libypclnt/Makefile			1.13
> src/lib/msun/Makefile				1.72
> src/secure/lib/libcrypto/Makefile		1.74
> src/secure/lib/libssh/Makefile		1.35
> src/secure/lib/libssl/Makefile		1.22
> src/usr.sbin/bsnmpd/modules/Makefile.inc	1.10

Reviewed by:	ru
Approved by:	re (scottl)

need for hack workarounds in tools/lib32/build32.sh.

via INCS.  Implemented INCSLINKS (equivalent to SYMLINKS) to
handle symlinking include files.  Allow for multiple groups of
include files to be installed, with the powerful INCSGROUPS knob.
Documentation to follow.

Added standard `includes' and `incsinstall' targets, use them
in Makefile.inc1.  Headers from the following makefiles were
not installed before (during `includes' in Makefile.inc1):

	kerberos5/lib/libtelnet/Makefile
	lib/libbz2/Makefile
	lib/libdevinfo/Makefile
	lib/libform/Makefile
	lib/libisc/Makefile
	lib/libmenu/Makefile
	lib/libmilter/Makefile
	lib/libpanel/Makefile

Replaced all `beforeinstall' targets for installing includes
with the INCS stuff.

Renamed INCDIR to INCSDIR, for consistency with FILES and SCRIPTS,
and for compatibility with NetBSD.  Similarly for INCOWN, INCGRP,
and INCMODE.

Consistently use INCLUDEDIR instead of /usr/include.

gnu/lib/libstdc++/Makefile and gnu/lib/libsupc++/Makefile changes
were only lightly tested due to the missing contrib/libstdc++-v3.
I fully tested the pre-WIP_GCC31 version of this patch with the
contrib/libstdc++.295 stuff.

These changes have been tested on i386 with the -DNO_WERROR "make
world" and "make release".