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.

1990/pjr/index.html

@@ -141,24 +141,24 @@ Location: <a href="../../location.html#GB">GB</a> - <em>United Kingdom of Great
 <!-- 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>
 <p>There is an <a href="#alternate-code">alternate version</a> that does something different
 that can be used if your compiler is incapable of compiling <code>X=g()...</code> in
 <code>main()</code>. It can be used for another purpose too.</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">./pjr</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./pjr</code></pre>
 <h2 id="alternate-code">Alternate code:</h2>
 <p>Note that some compilers will be unable to compile the expression <code>X=g()...</code> in
 <code>main()</code> due to lack of temporary stack space. One might want to try replacing
 <code>main()</code> with:</p>
-<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>    main<span class="op">(){</span>X<span class="op">=</span>s<span class="op">().</span>v<span class="op">().</span>o<span class="op">().</span>o<span class="op">().</span>l<span class="op">().</span>S<span class="op">().</span>d<span class="op">().</span>l<span class="op">().</span>i<span class="op">().</span>o<span class="op">().</span>w<span class="op">().</span>N<span class="op">();}</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    main(){X=s().v().o().o().l().S().d().l().i().o().w().N();}</code></pre>
 <p>if this is a problem, which is what this alternate code is.</p>
 <p>NOTE: it prints something else and it is what the author suggested one try as
 well.</p>
 <h3 id="alternate-build">Alternate build:</h3>
-<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> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <h3 id="alternate-use">Alternate use:</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="ex">./pjr.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./pjr.alt</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>This program prints out a string. Can you figure out how
 it is done?</p>
@@ -175,7 +175,7 @@ alphabetical character from a to z is printed out as its
 opposite:</p>
 <pre><code>    a-&gt;z b-&gt;y c-&gt;x etc</code></pre>
 <p>To encode a new string input the string as it is meant to come out:</p>
-<div class="sourceCode" id="cb7"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a>    X<span class="op">=</span>s<span class="op">().</span>v<span class="op">().</span>o<span class="op">().</span>o<span class="op">().</span>l<span class="op">().</span>S<span class="op">().</span>d<span class="op">().</span>l<span class="op">().</span>i<span class="op">().</span>o<span class="op">().</span>w<span class="op">().</span>N<span class="op">();</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    X=s().v().o().o().l().S().d().l().i().o().w().N();</code></pre>
 <p>Note: <code>S()</code> represents a space and <code>N()</code> a newline. This will now
 produce…</p>
 <pre><code>    hello world</code></pre>