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/otterness/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
@@ -18,14 +18,14 @@ For more detailed information see [2020 otterness bugs](../../bugs.html#2020_ott
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -74,7 +74,7 @@ for most of my testing (see [cvikl.mid](cvikl.mid)).
 Compile the program using the following command (I tested this using both
 `clang` and `gcc`):
 
-```sh
+```<!---sh-->
     cc -pedantic -Wall -Werror -Wextra -O3 -o prog prog.c
 ```
 

2020/otterness/index.html

@@ -141,15 +141,15 @@ 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>
 <h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
 <p>The current status of this entry is:</p>
 <pre><code>    STATUS: INABIAF - please **DO NOT** fix</code></pre>
 <p>For more detailed information see <a href="../../bugs.html#2020_otterness">2020 otterness bugs</a>.</p>
 <h2 id="to-use">To use:</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">./prog</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog</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>
 <p>Now play <code>output.mid</code> and <code>output2.mid</code> in an audio player that can play MIDI
 files.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
@@ -179,7 +179,7 @@ for most of my testing (see <a href="cvikl.mid">cvikl.mid</a>).</p>
 <h3 id="usage">Usage</h3>
 <p>Compile the program using the following command (I tested this using both
 <code>clang</code> and <code>gcc</code>):</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">cc</span> <span class="at">-pedantic</span> <span class="at">-Wall</span> <span class="at">-Werror</span> <span class="at">-Wextra</span> <span class="at">-O3</span> <span class="at">-o</span> prog prog.c</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    cc -pedantic -Wall -Werror -Wextra -O3 -o prog prog.c</code></pre>
 <p>The program expects a MIDI on <code>stdin</code>, and writes a modified MIDI to <code>stdout</code>:</p>
 <pre><code>    ./prog &lt;input.mid &gt;output.mid</code></pre>
 <p>If the program encounters an error, no output will generally be produced, and