Research on the meaning of the REQUEST_URI environment variable suggests that I've
been doing it wrong for a long time.  Findings:

  1.  REQUEST_URI is not part of
      So it isn't an official CGI variable.  Hence its meaning is not well-defined.

  2.  Apache and Nginx set REQUEST_URI to be the second field of the HTTP request.
      That means that REQUEST_URI includes the query string.

  3.  Althttpd and Wapp omit the query string from REQUEST_URI.

  4.  Fossil doesn't really care that much.  Fossil wants to use
      SCRIPT_NAME and PATH_INFO.  Fossil mostly only uses REQUEST_URI when one or the other of
      those two are unavailable.

We need to bring Fossil into agreement with Apache and Nginx.  That is what this branch is
about.  Althttpd and Wapp also need to be brought into conformance.