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.

1994/shapiro/index.html

@@ -430,16 +430,16 @@ this program. Note that this alt file is currently missing. See
 <p>The basic theme (pun) of this program is:</p>
 <pre><code>    &quot;This time (everything) is not where it should be.&quot;
           ~~~~</code></pre>
-<p>My entry (<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro.c">shapiro.c</a>) is mostly comments, formatted in the shape of a
+<p>My entry, <a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro.c">shapiro.c</a>, is mostly comments, formatted in the shape of a
 clock. If you strip out the comments and look at the code you will
 quickly realize that the comments were the important part and that
 the code does very little (see pun above). It writes (to <code>stdout</code>)
-another C program (<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro_t2.c">shapiro_t2.c</a>). This is the first level of
+another C program (<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro_t2.c">shapiro_t2.c</a>. This is the first level of
 obfuscation.</p>
 <p>The second program (<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro_t2.c">shapiro_t2.c</a> (use <code>make everything</code> first)
 prints a clock in the upper right hand corner of your VTxxx/ANSI display.</p>
-<p>Most of the surface obfuscation in the second program
-(<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro_t2.c">shapiro_t2.c</a>) was an attempt to make it as small as possible.
+<p>Most of the surface obfuscation in the second program,
+<a href="https://github.com/ioccc-src/temp-test-ioccc/blob/master/1994/shapiro/shapiro_t2.c">shapiro_t2.c</a>, was an attempt to make it as small as possible.
 You should be able to see around this with <code>cb(1)</code> and some more intelligent
 variable names. Once you get past this you will realize that the third level of
 obfuscation is a six member client/server hierarchy. (See the