Log message:
"user-destdir" is default these days

Log message:
Set BUILDLINK_ABI_DEPENDS correctly (with +=, not ?=)
It turns out there were a lot of these.

Log message:
Avoid picking up non-standard libm builtins with newer GCC

Log message:
DESTDIR support

Log message:
Mark packages as MAKE_JOBS_SAFE=no that failed in a bulk build with
MAKE_JOBS=2 and worked without.

Log message:
Convert @exec/@unexec to @pkgdir or drop it.

Log message:
Remove @dirrm entries from PLISTs

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:
MASTER_SITES (and HOMPAGE) gone away, change MASTER_SITE to site still have
this version.
Noticed by Zafer Aydogan via private mail.
HOMEPAGE also is changed to SourceForge project,
but it don't have old version though.

Log message:
Prepare for switching to NO_MTREE=yes.