Heimdal: Fix 32bit build problems

Heimdal: Fix 32bit build problems

The earlier inclusion of sha512 from Heimdal broke the build on
32bit platforms, because this file doesn't flag 64bit constants as
being such.

The correct place for this fix is in Heimdal, and it will be replaced
with a fix from Heimdal as soon as one is available. For now though,
this gets our build going again.

Change-Id: I0de822a933184078c491a16aafef45519fa2bbd2
Reviewed-on: http://gerrit.openafs.org/2901
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>