…- engine state already tracks these.

Salsa20Engine is refactored slightly to allow XSalsa20Engine to override key setup, algorithm name and nonce size.

XSalsa20 test vectors copied from CryptoPP (which generated them using nacl xsalsa20 implementation).

Test vectors generated with the reference implementations in estreambench-20080905.

…y setup, block counter and state permutation.

Standard 20 round, and reduced round variants are supported.
Test vectors for 20/12/8 round variants generated with reference implementation from estreambench-20080905.

This boosts speed on 64 bit Java 7, OS X Macbook Pro 2.5GHz Core i5 from 100MB/s (23 c/b) to 114MB/s (21 c/b) (measured on long streams).