Add support for "AES-256-CBC" encrypted private RSA key

[Joern Heissler]

Hi,
I created my private RSA key with openssl, it starts with:

-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-256-CBC,339DF1FA512279796DA0E92CC5EA41F9

Can you please add support for AES-256 encryption?

elif algo==b("AES-256-CBC"):
    key = PBKDF1(passphrase, salt[0:8], 16, 1, Crypto.Hash.MD5)
    key += PBKDF1(key+passphrase, salt[0:8], 16, 1, Crypto.Hash.MD5)
    keyobj = AES.new(key, Crypto.Cipher.AES.MODE_CBC, salt)

Or, as the code looks quite similar, make it more generic to work with all (?) algorithms:
key = b('')
while len(key) < keysize:
    key += PBKDF1(key+passphrase, salt[0:8], min(16, keysize - len(key)), 1, Crypto.Hash.MD5)
keyobj = cipher.new(key, cipher.MODE_CBC, salt)

Cheers!