When checking to see whether we have to rebind a new key and/or

When checking to see whether we have to rebind a new key and/or
certificate, the stored "previous value" is now the sum of the
existing key *and* certificate modification times.  This causes a
rebind to occur if either file's modification time is touched.
It does not matter if this rolls over on 32-bit systems because
we are only checking to see if the value changed, not for any
particular date comparison.