Make KCM the default ccache on OS X

If we do not find a default ccache value from krb5-config and we
detect that the host platform is OS X 10.7 or higher, use KCM: as the
default ccache name instead of FILE:/tmp/krb5cc_%{uid}.

https://github.com/krb5/krb5/commit/f2aabecc10508c01b289e147a4c5f41969ab768f
Author: Greg Hudson <ghudson@mit.edu>
Commit: f2aabecc10508c01b289e147a4c5f41969ab768f
Branch: master
 src/configure.in |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)