Bugfix: cpu: Correct results found by scrypt algorithm

- Fix scanhash_scrypt prototype in driver-cpu.c
- Always iterate over nonces in big-endian (since scrypt implementation works with big endian ints, this is faster)
- Always swap big-endian nonce to little-endian for "data" storage (expected format); thanks to Dmitry Eremin-Solenikov for reporting this issue
Merge commit 'c8b9cc4' into bfgminer