Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Add META_MODE support.

Off by default, build behaves normally.
WITH_META_MODE we get auto objdir creation, the ability to
start build from anywhere in the tree.

Still need to add real targets under targets/ to build packages.

Differential Revision: D2796
Reviewed by: brooks imp

Remove NO_OBJ

For meta mode we will want objdirs.

Differential Revision: D2748
Reviewed by: brooks imp

Use src.opts.mk in preference to bsd.own.mk except where we need stuff
from the latter.

MK_* variable should be compared to "no" not "NO".

Submitted by: "b.f." <bf1783@googlemail.com>

Don't install telnet.h if it will be installed by libtelnet.

Start the dreaded NOFOO -> NO_FOO conversion.

OK'ed by: core

For variables that are only checked with defined(), don't provide
any fake value.

Added new bsd.incs.mk which handles installing of header files
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".