Merge branch 'bug_fix_1209399' into scrypt
Resolve merge conflict between master and salsa20
Add support for scrypt

scrypt is a robust password-based key derivation function.
These set of changes implements it according to the RFC draft:

http://tools.ietf.org/html/draft-josefsson-scrypt-kdf-01

scrypt is also added to the algorithms understood by PKCS#8
(so that one can protect private keys at rest with it).

Additionally, this patch adds tests cases for PBES functions.
Optimize scrypt (~50%) and support for Python 2.1