Import of code from heimdal

Import of code from heimdal

This commit updates the code imported from the external
heimdal git repository to their revision
4f5390877a6cdb9615cf1f61f1884edc7b91522c
which is described as switch-from-svn-to-git-1447-g4f53908

Change-Id: I8a679232dfb25ba636600264b235667f06a5f62c
Reviewed-on: http://gerrit.openafs.org/2607
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>