fix more broken markdown links

We fix more markdown links in markdown files that refer to files
internally to the web site.

Added tmp tools to find and print various markdown links:

* `tmp/md-links.sh` - print all markdown links
* `tmp/md-token-links.sh` - print all markdown links that start with a **%%TOKEN%%**
* `tmp/md-local-links.sh` - print all markdown links to a local file
* `tmp/md-link-paths.sh` - print local file paths referenced in markdown links

Fixed a number of markdown formatting problems with `thanks-for-help.md`.
Fixed markdown links to files in `thanks-for-help.md`.  Improved
heading levels in `thanks-for-help.md`, and made entry sections consistent.

Changed all markdown links that end in "))" to end in a better way.

Explained in `markdown.md` why we are avoiding markdown links that
end in "))".

Ran `make www` to perform the above.

TODO: Fix stuff we broke by mistake doing the above.

TODO: Fix more broken markdown links.

2004/gavin/README.md

@@ -102,8 +102,8 @@ well as the judges' remarks below plus [gavin.html](gavin.html).
 ## Judges' remarks:
 
 Over the years, we've seen a program that immediately dumps core if executed on
-the "wrong" architectures (e.g., [1984/mullender](../../1984/mullender/index.html)) and a
-program that dumps core after a while (e.g., [2001/bellard](../../2001/bellard/index.html)).
+the "wrong" architectures (e.g., [1984/mullender](../../1984/mullender/index.html) entry) and a
+program that dumps core after a while (e.g., [2001/bellard](../../2001/bellard/index.html) entry).
 This entry will happily compile and execute on most any architecture - the trick
 is that the result, to be useful, must be produced (and can only be enjoyed) on
 a particular architecture.  We have not decided yet whether to disallow this for

2004/gavin/index.html

@@ -441,8 +441,8 @@ generated are the same names. See <a href="#to-use">to use</a> and <a href="#try
 well as the judges’ remarks below plus <a href="gavin.html">gavin.html</a>.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Over the years, we’ve seen a program that immediately dumps core if executed on
-the “wrong” architectures (e.g., <a href="../../1984/mullender/index.html">1984/mullender</a>) and a
-program that dumps core after a while (e.g., <a href="../../2001/bellard/index.html">2001/bellard</a>).
+the “wrong” architectures (e.g., <a href="../../1984/mullender/index.html">1984/mullender</a> entry) and a
+program that dumps core after a while (e.g., <a href="../../2001/bellard/index.html">2001/bellard</a> entry).
 This entry will happily compile and execute on most any architecture - the trick
 is that the result, to be useful, must be produced (and can only be enjoyed) on
 a particular architecture. We have not decided yet whether to disallow this for