Test vectors for SHA224,256,384 and 512 have been
generated using Python's hashlib module by the
following oneliner:

import binascii, hashlib
binascii.hexlify(hashlib.pbkdf2_hmac(ALGO, binascii.unhexlify('PASSWORD'), binascii.unhexlify('SALT'), ITER, KEYLEN)))

where ALGO was 'sha224', 'sha256', 'sha384' and 'sha512'
respectively.

Values for PASSWORD, SALT, ITER and KEYLEN were copied from the
existent test vectors for SHA1.

For SHA256 we also have two test vectors coming from RFC7914 Sec 11.

Signed-off-by: Antonio Quartulli <antonio@openvpn.net>