create debugging kext package for MacOS

create debugging kext package for MacOS

this creates and installs a debugging kext package for macos. it also
always installs the decode-panic script (which can be used even without
the debug kext)

Change-Id: Iff03de66cd3df2690f03333e6629d21660364cd1
Reviewed-on: http://gerrit.openafs.org/1120
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit cc47e765912e1a5dedddb6ef00ca8b8c8d567f0e)
Reviewed-on: http://gerrit.openafs.org/1214