Implement the eksBlowfish function
Implement the eksBlowfish function

This modifies the standard blowfish key schedule function to accept an
optional salt and cost as used in bcrypt and modifies the algorithm
accordingly to implement the "expensive" version.

The standard blowfish version is just the same but with a salt value of
zero and a single call to the expandKey function. See the original
bcrypt paper for more details.

tekul/cryptonite,nomeata/cryptonite,tekul/cryptonite,vincenthz/cryptonite,nomeata/cryptonite