Re: Refactor digest authentication in url-auth

[Jarno Malmari]

Here's a revised patch set for the earlier digest auth work.

* Changed comments to follow gnu coding standards: two spaces between
  sentences, capital letter at beginning, period at the end, and the
  like

* Removed bunch of references to RFC 2617 from docstrings. Still to
  understand what's being done requires you to pick that up, but
  mentioning it repeatedly doesn't help too much.

* Changed the format of commit messages.

* There were talk about what to call the "path component of an URI".
  Is it file-name part, directory, path, or URI path. I tried avoiding
  mentioning it but a few references remains and I ended up choosing
  "directory" since that's what's used in functions used here, namely:

    (url-file-directory (url-filename url))

  The `url-file-directory' is defined in url-util with docstring:

     "Return the directory part of FILE, for a URL."

Patches that follows:
[PATCH 1/2] Refactor digest authentication in url-auth
[PATCH 2/2] Initial implementation for HTTP Digest qop for url