Add a sanity check to the print_bin function to ensure that the |off|
argument is positive. Thanks to Kevin Wojtysiak (Int3 Solutions) and
Paramjot Oberoi (Int3 Solutions) for reporting this issue.
Reviewed-by: Andy Polyakov <appro@openssl.org>
(cherry picked from commit 3deeeeb61b0c5b9b5f0993a67b7967d2f85186da)