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.

1993/ejb/index.html

@@ -141,13 +141,13 @@ Location: <a href="../../location.html#ZZ">ZZ</a> - <em>Unknown location</em></l
 <!-- 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">./ejb</span> level</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./ejb level</code></pre>
 <p>where:</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">level</span>   a value from <span class="at">-128</span> to 127</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    level   a value from -128 to 127</code></pre>
 <h2 id="try">Try:</h2>
-<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">./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>A negative argument plays the patience puzzle. An argument
 greater than 0 plays the Tower of Hanoi puzzle. In either case
@@ -160,11 +160,11 @@ the argument 127 to this program and want to see it finish!</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="what-this-program-does">What this program does</h3>
 <h4 id="output-solution-to-towers-of-hanoi-for-five-rings">Output solution to Towers of Hanoi for five rings:</h4>
-<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="ex">./ejb</span> 5</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./ejb 5</code></pre>
 <p>The format of the output for the Towers of Hanoi case is simply a
 text description of how to solve the puzzle.</p>
 <h4 id="output-solution-to-the-patience-puzzle-for-six-rings">Output solution to the Patience puzzle for six rings:</h4>
-<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">./ejb</span> <span class="at">-6</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./ejb -6</code></pre>
 <p>For the patience puzzle, the output is a sequence binary codes representing
 successive states of the puzzle. The rightmost digit represents the first ring.
 A <code>1</code> means the ring is on the <code>U</code>; a <code>0</code> means it is off the <code>U</code>. The program