Modernize code

[wens]

Some ideas to modernize the code:

• Use arc4random and co.
• Re-align structures and drop the packed attribute
• Use crypt_r w/ SHA256 or SHA512
• IPv6 support?

[mshockwave]

Just as a follow-up comment:
Though it's not so straight forward, but we definitely need testings

[hungte]

I think we're probably all done (or, nothing to do) here?

1. arc4random : already used.
2. Re-align structures and drop the packed attribute: partially, but for C network stream I see no reason to "drop pack".
3. crypt_r is replaced by fcrypt (blow fish) so no need to do SHA256/512 etc.
4. IPv6 seems already supported (or not needed) since mbbsd now only takes input from the sshd or ws?

[wens]

Our production environment doesn't have IPv6, so for us it's not needed. However I am sure there are address (string or binary) fields that are not large enough for actual IPv6 usage.