Bugfix
   * Fix bug in conversion from OID to string in
     mbedtls_oid_get_numeric_string(). OIDs such as 2.40.0.25 are now printed
     correctly.
   * Reject OIDs with overlong-encoded subidentifiers when converting
     them to a string.
   * Reject OIDs with subidentifier values exceeding UINT_MAX.  Such
     subidentifiers can be valid, but Mbed TLS cannot currently handle them.
   * Reject OIDs that have unterminated subidentifiers, or (equivalently)
     have the most-significant bit set in their last byte.