add hack-a-round for language specified markdown code blocks

When language is specified in a markdown code block such as:

````
```c
    printf("Hello, world!\n");
```
````

is used, the resulting HTML as produced by `pandoc(1)` combined
with our revised `ioccc.css` is not intent the code block well.

A temporary "_hack-a-round_" is to turn the "markdown code language
specifier" into an HTML comment.  For example:

````
```<!---c-->
    printf("Hello, world!\n");
```
````

This commits turns off existing markdown code language specifiers
for now, while preserving our ability to restore them in the future
when a better  "_hack-a-round_" to the "markdown code language
specifier" problem is found.

The HTML impact if this "_hack-a-round_" is to produce HTML that
looks like this:

```
<pre class="&lt;!---c--&gt;"><code> .. </code></pre>
```

We might be able to create a complex set of classes for each markdown
code language (there won't be very many) in `ioccc.css`, or we might
find a more general CSS (or maybe `pandoc(1)`?) solution.

For now, this hack-a-round will have to do.

1991/ant/index.html

@@ -141,18 +141,18 @@ Location: <a href="../../location.html#CA">CA</a> - <em>Canada</em></li>
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
 <h2 id="to-build">To build:</h2>
-<div class="sourceCode" id="cb1"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make all</code></pre>
 <p>There is an <a href="#alternate-code">alternate version</a> that might feel a bit more
 familiar to vi(m) users.</p>
 <h2 id="to-use">To use:</h2>
-<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./ant</span> some_file</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./ant some_file</code></pre>
 <p>NOTE: the file must already exist and not specifying any arg will make the
 program exit without doing anything.</p>
 <h2 id="try">Try:</h2>
-<div class="sourceCode" id="cb3"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> hill</span>
-<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./ant</span> hill</span></code></pre></div>
-<div class="sourceCode" id="cb4"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> mole</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./ant</span> mole</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make hill
+    ./ant hill</code></pre>
+<pre class="&lt;!---sh--&gt;"><code>    make mole
+    ./ant mole</code></pre>
 <h2 id="alternate-code">Alternate code:</h2>
 <p>This version changes the commands slightly so that to go to the first column you
 should enter <code>0</code>, to go to the last column you should enter <code>$</code>, to quit you
@@ -163,7 +163,7 @@ ESC (<code>\x1b</code>).</p>
 <p>These will make it slightly less unwieldy for those familiar with vi(m); the
 rest was unchanged.</p>
 <h3 id="alternate-build">Alternate build:</h3>
-<div class="sourceCode" id="cb5"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <h3 id="alternate-use">Alternate use:</h3>
 <p>Use <code>ant.alt</code> as you would <code>ant</code> above with the changes in the input keys. See
 the author’s remarks for the remaining keys.</p>