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.

bugs.html

@@ -407,7 +407,7 @@ it takes away some instructional value or even usability. _In this case we’re
 <strong>VERY SORRY</strong> about it: it’s a fine line, we know, and we tried to use careful
 judgement but invariably some might have been the wrong decision. Thank you for
 understanding!</p>
-<p>I (<a href="authors.html#Cody_Boone_Ferguson">Cody Boone Ferguson</a>)
+<p>I ( <a href="authors.html#Cody_Boone_Ferguson">Cody Boone Ferguson</a> )
 accept the blame in some cases; when working on getting entries to compile
 sometimes I got carried away with it and there might be that I fixed some things
 that should not have been fixed. I am correcting these mistakes as I come across
@@ -1793,7 +1793,7 @@ crash this makes sense.</p>
     -0.0515873015873016</code></pre>
 <p>and that’s what it shows in linux.</p>
 <p>Note that with different perl libraries in macOS (for instance from
-<a href="https://brew.sh">Homebrew</a> and <a href="https://www.macports.org">MacPorts</a>) it will
+<a href="https://brew.sh">Homebrew</a> and <a href="https://www.macports.org">MacPorts</a> package managers) it will
 likely print different warnings when compiling. It was observed that with
 Homebrew it does not report any warnings but with MacPorts it results in a total
 of 92 warnings! Nonetheless neither works okay and both crash.</p>