mod_auth_digest fixes:

- better comparing of request-uri with uri parameter in Authorization
  header
- added a check for a MUST condition in the spec
- fixed SEGV


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@84253 13f79535-47bb-0310-9956-ffa450edef68