Replace strnlen with strlen

The GNU extension is not defined on OS X and not necessary in any case.
Use server functions for "hello" service

Replaces the libmicrohttpd example code with a similar minimal example
using the routing and server framework. Responds like:

  > GET /hello
  > Accept: text/html

  < HTTP/1.1 200 OK
  < Content-Type: text/html
  <
  < <html>...</html>

  > PUT /hello
  > Content-Type: text/plain

  < HTTP/1.1 204 No Content

  > POST /hello

  < HTTP/1.1 201 Created
  < Location: /hello

Many previously static functions were made public for things to work,
should probably revisit the function organization as a consequence.
Add test endpoint that takes a path argument

GET /evens/{n} returns HTML with the value of n in the body for even n
and 404's otherwise. This revealed some fuzziness in what exactly was
being found by the "find resource" behavior, the upshot being the
introduction of a found_resource structure that links to the resource
definition as well as an optional blob of arbitrary data that can be
used in the respond method.
Remove configure from source control