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.

1987/korn/index.html

@@ -141,9 +141,9 @@ 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> 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">./korn</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./korn</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>The Judges believe that this is the best one line entry ever received.
 Compile on a UNIX system, or at least one using a C implementation that
@@ -158,17 +158,17 @@ section right now and see if you are one of the few people who can.</p>
 <li><p>What is the value of the symbol <code>"have"</code>? (hint: the value is NOT 4
 characters, or <code>'h'</code>, or a string) Consider the fact that:</p></li>
 </ol>
-<div class="sourceCode" id="cb3"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>    <span class="dt">char</span> <span class="op">*</span>x<span class="op">;</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    char *x;</code></pre>
 <p>defines a pointer to a <code>char</code> (i.e. an address), and that the <code>=</code> assigns
 things of compatible types. Since:</p>
-<div class="sourceCode" id="cb4"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>    x <span class="op">=</span> <span class="st">&quot;have&quot;</span><span class="op">;</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    x = &quot;have&quot;;</code></pre>
 <p>is legal C, what type of value is <code>"have"</code>?</p>
 <ol start="3" type="1">
 <li>Note that the following expressions yield the same value:</li>
 </ol>
-<div class="sourceCode" id="cb5"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a>    x<span class="op">[</span><span class="dv">3</span><span class="op">]</span>        <span class="op">*(</span>x<span class="op">+</span><span class="dv">3</span><span class="op">)</span>    <span class="op">*(</span><span class="dv">3</span><span class="op">+</span>x<span class="op">)</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    x[3]        *(x+3)    *(3+x)</code></pre>
 <p>since addition is commutative. What can be said about this value?</p>
-<div class="sourceCode" id="cb6"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>    <span class="dv">3</span><span class="op">[</span>x<span class="op">]</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    3[x]</code></pre>
 <p><a href="https://news.slashdot.org/story/01/02/06/2030205/david-korn-tells-all">David
 Korn</a>’s
 <a href="https://en.wikipedia.org/wiki/KornShell">/bin/ksh</a> provides us with a greatly