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.

1985/README.md

@@ -6,7 +6,7 @@ and try to figure how it does what it does!  You may then wish to look at the
 Author's remarks for even more details.
 
 Hints against machine dependent code were added to the [rules](rules.txt) to
-avoid another 1984 style entry ([1984/mullender](../1984/mullender/index.html)).
+avoid another 1984 style [1984/mullender](../1984/mullender/index.html) entry.
 [Rules](rules.txt) and [results](../years.html#1985) were posted to _net.lang.c_
 and _net.unix-wizards_.  Larry Bassel was invited to help in the judging.
 Awards were given to 5 classes of programs since we were unable to select only