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.

2001/cheong/index.html

@@ -141,11 +141,11 @@ 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></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make</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">./cheong</span> digits</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./cheong digits</code></pre>
 <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="ex">./try.sh</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./try.sh</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Be sure to give an even number of digits in the argument. Add a
 leading 0 if needed.</p>
@@ -156,17 +156,17 @@ as all good programs should be! :-)</p>
 <p>Compile normally and run with one argument, an integer with 2n digits.
 Program will return the integer part of its square root (n-digits).
 For example,</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">$</span> cc <span class="at">-o</span> cheong cheong.c</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">$</span> ./cheong 1234567890</span>
-<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a>    <span class="ex">35136</span></span>
-<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a>    <span class="ex">$</span> ./cheong 0200000000000000000000000000</span>
-<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a>    <span class="ex">14142135623730</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    $ cc -o cheong cheong.c
+    $ ./cheong 1234567890
+    35136
+    $ ./cheong 0200000000000000000000000000
+    14142135623730</code></pre>
 <p>Deviation from these instructions will cause undefined results. :-)</p>
 <h3 id="portability">Portability</h3>
 <p>This program runs normally on any ANSI C compiler and is ASCII dependent.</p>
 <p>Strict compiling gives just one unavoidable warning:</p>
-<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">gcc</span> <span class="at">-ansi</span> <span class="at">-Wall</span> cheong.c</span>
-<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">cheong.c:3:</span> warning: third argument of <span class="kw">`</span><span class="ex">main</span><span class="st">&#39; should probably be `char **&#39;</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    gcc -ansi -Wall cheong.c
+    cheong.c:3: warning: third argument of `main&#39; should probably be `char **&#39;</code></pre>
 <h3 id="obfuscation">Obfuscation</h3>
 <p>The main obfuscation is the algorithm used to calculate square roots,
 sometimes known as the longhand method. The basic algorithm is itself