osx: decode-panic should work in add-kext only land

osx: decode-panic should work in add-kext only land

in 64 bit 10.6, you need add-kext (not add-symbol-file)
to decode a panic. deal accordingly

Reviewed-on: http://gerrit.openafs.org/4255
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit c4744cc699be19fffb49f39f469e91ef6aac6585)

Change-Id: I3de2c4799ff1a552e67d4398b76e8736ba2abf7e
Reviewed-on: http://gerrit.openafs.org/4268
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>