examples: add systemtap script to ease lock debugging
    
    As discussed before, this simple script should help with debugging
    deadlocks, although there are still some caveats.  RWLocks are not
    handled by this and if your deadlock if very racy, it may not lock
    up when running with this script due to the slowdown.
    
    Signed-off-by: Martin Kletzander <mkletzan@redhat.com>