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.

2006/sloane/index.html

@@ -141,31 +141,31 @@ Location: <a href="../../location.html#US">US</a> - <em>United States of America
 <!-- 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> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <p>We recommend the alt version so that you can see what this looked like back in 2006.
 If you wish to see the original faster version see <a href="#original-code">original
 code</a> below.</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">./slone.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./slone.alt</code></pre>
 <h2 id="try">Try:</h2>
 <p>The alternate version, which we recommend that you use in order to see what is
 happening with modern systems, and to not flash too quickly, which can be
 problematic for some people, can be configured to different speeds by way of the
 value used in <code>usleep()</code>. The default is <code>75000</code> but you can easily change
 it. To do so try:</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="fu">make</span> clobber SLEEP=70000 clobber alt</span>
-<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./sloane.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make clobber SLEEP=70000 clobber alt
+    ./sloane.alt</code></pre>
 <p>If you wish to make it like the original, as if the below <a href="#original-code">Original
 code</a> was being used, you can do:</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="fu">make</span> SLEEP=0 clobber alt</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./sloane.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make SLEEP=0 clobber alt
+    ./sloane.alt</code></pre>
 <h2 id="original-code">Original code:</h2>
 <p>Should you wish to see the original you may do so with the original code,
 <a href="sloane.c">sloane.c</a>.</p>
 <h3 id="original-build">Original 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> clobber all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make clobber all</code></pre>
 <h3 id="original-use">Original use:</h3>
-<div class="sourceCode" id="cb6"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./sloane</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./sloane</code></pre>
 <p>WARNING: if you are easily overstimulated with fast movement or have
 photosensitivity please be careful running this version and instead see the
 above!</p>