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:
Set MAKE_JOBS_SAFE=no

Log message:
Convert to use PLIST_VARS instead of manually passing "@comment "
through PLIST_SUBST to the plist module.

Log message:
Fix configure options when the librack option is given.
This fixes the second problem in PR 36617.

Log message:
Make this build with db4.  This fixes the first problem in PR 36617.

Log message:
pkgsrc added --without-libcrack to CONFIGURE_ARGS if libcrack is missing
from PKG_OPTIONS, and also comments out the libcrack module in the PLIST.
However this means nothing to the PAM configure script, which will find a
system libcrack and install the libcrack module.  When the pkgsrc bulk
build deinstalls PAM, it detects the leftover libcrack module and marks
PAM and its dependents failed.

Fix this by adding a --disable-crack option to the configure script.

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.

Log message:
Do not install files directly into etc; it should be handled through
CONF_FILES.

Log message:
Honor CPPFLAGS.  This is a fix for pkgsrc libtoolization, so there is no
need to notify the author.