Log message:
Upgrading Xfce to 4.6.1.

This is for PR #40984. This is based on work from
dieter roelants. Thank you Dieter.
Also I had done some work independently on this.
Hopefully, I am getting this all committed at one time.

The changelogs are at
http://www.xfce.org/documentation/changelogs/4.6.1
http://www.xfce.org/documentation/changelogs/4.6.0

Also don't need the xfce4-dev-tools for building. (It is only
needed when building from SVN source.)

Log message:
bump revision because of graphics/jpeg update

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:
Bump BUILDLINK_{API,ABI}_DEPENDS.
Bump PKGREVISION (some packages ride the previous PKGREVISION bump).

Log message:
Fix PLIST again.

Log message:
Add missing entries to PLIST.  Bump PKGREVISION.