This silences a warning message that was printed to the console whenever
this module was loaded during tests.
The API changes between these two versions were reviewed carefully for
differences. The only difference made was to `PBKDF2_HMAC_SHA256.bytes`,
which was replaced by `Pbkdf2HmacSha256`.
The length argument no longer has a default value, so it has been set
to match what the default value was in the previous version we used,
which is 32 (the SHA256 hash size).
Mark Stacey
bitpshr
Csaba Solya