Log message:
Simply and speed up buildlink3.mk files and processing.
This changes the buildlink3.mk files to use an include guard for the
recursive include. The use of BUILDLINK_DEPTH, BUILDLINK_DEPENDS,
BUILDLINK_PACKAGES and BUILDLINK_ORDER is handled by a single new
variable BUILDLINK_TREE. Each buildlink3.mk file adds a pair of
enter/exit marker, which can be used to reconstruct the tree and
to determine first level includes. Avoiding := for large variables
(BUILDLINK_ORDER) speeds up parse time as += has linear complexity.
The include guard reduces system time by avoiding reading files over and
over again. For complex packages this reduces both %user and %sys time to
half of the former time.

Log message:
Add MAKE_JOBS_SAFE after noticing a the build wanted a library
it had yet to make.

Log message:
Add DESTDIR support, fixing normal installation as well.

Log message:
PR 37949: Aleksey Cheusov: USE_TOOLS needs to be fixed in several packages

Log message:
Do not unconditionally remove share/sgml/jade, tex-jadtex uses it too.
Bump PKGREVISION.

Log message:
Fixed some pkglint warnings.

Log message:
There is no package called "sp", so remove the useless paragraph.

Log message:
Drop support for LTCONFIG_OVERRIDE.  For quite a long time, pkgsrc
had actually been ignoring LTCONFIG_OVERRIDE anyway and just using
the default LIBTOOL_OVERRIDE to replace libtool scripts in packages.
This just formalizes the fact that LTCONFIG_OVERRIDE is not used
meaningfully by pkgsrc.

Log message:
Change the format of BUILDLINK_ORDER to contain depth information as well,
and add a new helper target and script, "show-buildlink3", that outputs
a listing of the buildlink3.mk files included as well as the depth at
which they are included.

For example, "make show-buildlink3" in fonts/Xft2 displays:

	zlib
	fontconfig
	    iconv
	    zlib
	    freetype2
	    expat
	freetype2
	Xrender
	    renderproto

Log message:
Track information in a new variable BUILDLINK_ORDER that informs us
of the order in which buildlink3.mk files are (recursively) included
by a package Makefile.