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.

README.html

@@ -421,7 +421,7 @@ programming practice, then to what depths might quality sink if people really
 tried to write poor code?</p>
 <p>I put that question to the USENET news groups net.lang.c and net.unix-wizards in
 the form of a contest. I selected a form similar to the contest
-(<a href="https://www.bulwer-lytton.com">Bulwer-Lytton</a>) that asks people to create the
+(<a href="https://www.bulwer-lytton.com">Bulwer-Lytton</a> contest) that asks people to create the
 worst opening line to a novel (that contest in turn was inspired by disgust over
 <a href="https://en.wikipedia.org/wiki/Paul_Clifford">a novel</a> by <a href="https://en.wikipedia.org/wiki/Edward_Bulwer-Lytton">Edward
 Bulwer-Lytton</a> that opened