Add more http statuses

[n00p3]

I needed to use status 422 - Unprocessable Entity and notices it's not present in hunchentoot so I've added it and a few others.

[metayan]

Thanks for adding the status codes.
418 caught my eye, and even though I like that it's called +http-im-a-teapot+ here, and agree with keeping it that way, it might be good to be aware of the current status of that status code (pun intended):

15.5.19.  418 (Unused)

   [RFC2324] was an April 1 RFC that lampooned the various ways HTTP was
   abused; one such abuse was the definition of an application-specific
   418 status code.  In the intervening years, this status code has been
   widely implemented as an "Easter Egg", and therefore is effectively
   consumed by this use.
   Therefore, the 418 status code is reserved in the IANA HTTP Status
   Code Registry.  This indicates that the status code cannot be
   assigned to other applications currently.  If future circumstances
   require its use (e.g., exhaustion of 4NN status codes), it can be re-
   assigned to another use.

IETF source
diff from when 418 was added