The SymmetricKey.Usage class has been converted into an
enumeration that defines the same elements. These elements
store the corresponding PKCS #11 CKF_ and CKA_ values
although the CKA_ values are not actually used.

The getVal() and getPKCS11Constant() method have been
deprecated, but they will continue to work as before for
backward compatibility.

The opFlags field in PK11KeyGenerator has been converted
to long to match the PKCS #11 value. The value will be
downcasted to int whenever needed.

The opFlagForUsage array in PK11KeyGenerator has become
redundant since the PKCS #11 value can be obtained from
the enumeration elements, so it has been removed.