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.

2019/adamovsky/index.html

@@ -141,15 +141,15 @@ Location: <a href="../../location.html#CZ">CZ</a> - <em>Czech Republic</em> (<em
 <!-- 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#2019_adamovsky">2019 adamovsky 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> file.unl</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog file.unl</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>Even after pre-processing and indenting, the C code of this entry it
 is about as understandable as the Unlambda code.</p>
@@ -159,7 +159,7 @@ bytes which crashed it:</p>
 <pre><code>    ````.0`.0`.0`c.0``sssss</code></pre>
 <p>Functional programming is not a panacea against core dumps, after all.</p>
 <p>This can be demonstrated by:</p>
-<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">./prog</span> crash.unl</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog crash.unl</code></pre>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="a-highly-structured-state-state-machine">A highly structured state state machine</h3>
 <h3 id="purpose">Purpose:</h3>
@@ -181,11 +181,11 @@ actually a <code>one-liner</code>. It certainly was for me. I like to think the
 by the sheer length of the dividing line and totally overlooks the rest of the program.</p>
 <h3 id="usage">Usage:</h3>
 <p>When built directly using</p>
-<div class="sourceCode" id="cb7"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make</code></pre>
 <p>the program (<code>prog</code>) accepts a single parameter with the name of an Unlambda program. You can
 download the <a href="https://github.com/irori/advent-unlambda" title="Adventure">Colossal Cave Adventure</a> (the <a href="advent.unl">advent.unl</a> file)
 and run it like this:</p>
-<div class="sourceCode" id="cb8"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span> advent.unl</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog advent.unl</code></pre>
 <blockquote>
 <p>NOTE: the file was added to the entry so there is no need to download it.</p>
 </blockquote>
@@ -194,7 +194,7 @@ and run it like this:</p>
 entries from <a href="http://www.madore.org/~david/programs/unlambda/#quine" title="Unlambda quine contest">quine contest</a>.</p>
 <p>There is an alternative build path that requires the 2018 IOCCC size tool to complete. Put the tool
 source <a href="iocccsize_2018.c">iocccsize_2018.c</a> in the project directory and call</p>
-<div class="sourceCode" id="cb9"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a>    <span class="fu">make</span> identify</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make identify</code></pre>
 <p>It will build the tool and use it to build an alternative program <code>prog2</code>, which in turn will
 produce an Unlambda program <code>identify.unl</code>. <code>make identify</code> runs this program to identify
 itself.</p>