MFC r314654:

cddl: normalize paths using SRCTOP-relative paths or :H when possible

This simplifies make logic/output

While here, remove bogus CFLAGS which look for headers in cddl/lib/libumem.
There aren't any source files there (just Makefiles)

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

META MODE: Fix userland/cddl.

MK_CTF controls whether ctfmerge is ran against the binaries, not
whether CTF tools should be built.

Sponsored by: EMC / Isilon Storage Division

META_MODE: Remove DEP_RELDIR from Makefile.depend files.

This has not been needed since r284171 in projects/bmake.

Sponsored by: EMC / Isilon Storage Division

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

Convert cftmerge to LIBADD and remove link on libdwarf which is not needed

These CTF tools do not use anything from libctf, so no need to link with it.

Remove trailing whitespace.

Add man pages for the CTF tools.

Sponsored by: The FreeBSD Foundation

Remove manual .includes in cddl Makefiles

- Break the dependency on ../Makefile.inc for .PATH, and include
../Makefile.inc implicitly. This is required to ...
- Set WARNS?=6 in top-level Makefile.inc
- Remove now redundant WARNS settings, add WARNS?=0 where appropriate
- Remove redundant SHLIB_MAJOR overrides
- Use NO_MAN, not MK_MAN=no
- Remove redundant inclusion of bsd.own.mk
- Order Makefiles more according to style.Makefile(9)
- Reduce diff of cddl Makefiles against each other

No objection: pjd
Approved by: ed (co-mentor)

Fixed dependencies (make checkdpadd).

Add the DTrace build tools.