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.

2020/ferguson1/crazy.log.html

@@ -123,7 +123,7 @@
 <!-- START: this line starts content for HTML phase 21 by: bin/pandoc-wrapper.sh via bin/md2html.sh -->
 
 <p>The following are a few screen dumps of:</p>
-<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="va">SIZE</span><span class="op">=</span>100 <span class="va">SHEDS</span><span class="op">=</span>5 <span class="va">GROW</span><span class="op">=</span>-10 <span class="va">SHED</span><span class="op">=</span>50 <span class="va">MAXSIZE</span><span class="op">=</span>250 <span class="ex">./prog</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    SIZE=100 SHEDS=5 GROW=-10 SHED=50 MAXSIZE=250 ./prog</code></pre>
 <p>As you will see it took 17 bugs to get down to below 0. Notice how I had to get
 down to 0 more than once: because I moved enough times before I got the last
 bug that I grew by 5 in size. I then however moved a bit more and ate a bug