macos: packaging support for MacOS X 10.14

macos: packaging support for MacOS X 10.14

This commit introduces the new set of changes / files required to
successfully create the dmg installer on OS X 10.14 "Mojave".

Reviewed-on: https://gerrit.openafs.org/13349
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
(cherry picked from commit 2aeabf8c5bca22b400653e2bc88b6f36d47b05ca)

Change-Id: Ia271ca69d8102a93da50c59e2d92d3c803a13b0e
Reviewed-on: https://gerrit.openafs.org/13413
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>