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/dds/index.html

@@ -141,18 +141,18 @@ Location: <a href="../../location.html#GR">GR</a> - <em>Hellenic Republic</em> (
 <!-- 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>
 <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">./dds</span> basic_program</span>
-<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span> <span class="dv">2</span><span class="op">&gt;</span>/dev/null</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./dds basic_program
+    ./a.out 2&gt;/dev/null</code></pre>
 <h2 id="try">Try:</h2>
 <p>The author suggests trying:</p>
-<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="ex">./dds</span> LANDER.BAS</span>
-<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./dds LANDER.BAS
+    ./a.out</code></pre>
 <p>Notice that a file <code>a.c</code> has been generated. Can you tell how <code>a.c</code> was
 produced? How does <code>a.c</code> relate to <a href="LANDER.BAS">LANDER.BAS</a>?</p>
 <p>What happens if you give the program a C program like itself? Try:</p>
-<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="ex">./dds</span> dds.c</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./dds dds.c</code></pre>
 <p>You’ll get errors yes but what does the generated file look like? What about
 other types of files?</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>