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.

2011/toledo/README.md

@@ -18,7 +18,7 @@ Windows](%%REPO_URL%%/2011/toledo/toledo.alt2.c). See [Alternate code](#alternat
 ```
 
 
-## Alternate code:
+## Alternate code
 
 The first alt version, [toledo.alt.c](%%REPO_URL%%/2011/toledo/toledo.alt.c), allows you to reconfigure
 the controls and the dimensions more easily.
@@ -191,7 +191,7 @@ Not really, just kidding :D
 * It is written in the only true C: K&R, and no, that doesn't mean
   Katherine & Rose.
 * Vectorial scalable graphics: do you want a bigger viewport? Change variables
-  `M` and `N` (see the [alternate code](#alternate-code)).
+  `M` and `N` (see the [alternate](#alternate-code) code).
 * Half of the program is formatted as 3D cube. View with tabs at 8 columns and a
   square font.
 * The other half of the program is unprintable source code, so no typing from

2011/toledo/index.html

@@ -405,7 +405,7 @@ controls and size</a> and <a href="https://github.com/ioccc-src/temp-test-ioccc/
 Windows</a>. See <a href="#alternate-code">Alternate code</a> below.</p>
 <h2 id="to-use">To use:</h2>
 <pre><code>    ./toledo</code></pre>
-<h2 id="alternate-code">Alternate code:</h2>
+<h2 id="alternate-code">Alternate code</h2>
 <p>The first alt version, <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2011/toledo/toledo.alt.c">toledo.alt.c</a>, allows you to reconfigure
 the controls and the dimensions more easily.</p>
 <p>The second version, <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/2011/toledo/toledo.alt2.c">toledo.alt2.c</a>, should work for Windows but
@@ -527,7 +527,7 @@ x86-64 512 MB).</li>
 <li>It is written in the only true C: K&amp;R, and no, that doesn’t mean
 Katherine &amp; Rose.</li>
 <li>Vectorial scalable graphics: do you want a bigger viewport? Change variables
-<code>M</code> and <code>N</code> (see the <a href="#alternate-code">alternate code</a>).</li>
+<code>M</code> and <code>N</code> (see the <a href="#alternate-code">alternate</a> code).</li>
 <li>Half of the program is formatted as 3D cube. View with tabs at 8 columns and a
 square font.</li>
 <li>The other half of the program is unprintable source code, so no typing from