Update the crypto(4) and crypto(9) manpages.

There are probably bits that are still wrong, but this fixes some
things at least:

• Add named arguments to the functions in crypto(9).
• Add missing algorithms.
• Don't mention arguments that don't exist in crypto_register.
• Add CIOGSESSION2.
• Remove CIOCNFSESSION.
• Clarify some stale language that assumed an fd had only one sesson.
• Note that you have to use CRIOGET and add a note in BUGS lamenting that one has to use CRIOGET.
• Various other cleanups.

Reviewed by: cem (earlier version)
MFC after: 2 weeks
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D22784