All changes affect only SCTP-AUTH:
* Remove non working code related to SHA224.
* Remove support for non-standardised HMAC-IDs using SHA384 and SHA512.
* Prefer SHA256 over SHA1.
* Minor cleanup.

MFC after: 2 weeks
Whitespace cleanup.
Use uint16_t instead of in_port_t for consistency with the SCTP code.

MFC after: 1 week