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.

2004/arachnid/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
@@ -11,20 +11,20 @@ code](#alternate-code) below.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./arachnid [mazefile]
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./arachnid arachnid.txt
 ```
 
 and then try:
 
-```sh
+```<!---sh-->
     ./arachnid arachnid.c
 ```
 
@@ -41,7 +41,7 @@ instead.
 
 ### Alternate build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
@@ -80,7 +80,7 @@ explorers out there.
 
 ### Usage
 
-```sh
+```<!---sh-->
     ./arachnid [mazefile]
 ```
 

2004/arachnid/index.html

@@ -141,16 +141,16 @@ Location: <a href="../../location.html#NZ">NZ</a> - <em>New Zealand</em></li>
 <!-- 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>
 <p>There is an alt version for rogue players, vi(m) users and Dvorak typist (i.e.
 those who need <code>hljk</code> for moving left, right, down and up. See <a href="#alternate-code">alternate
 code</a> below.</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">./arachnid</span> <span class="pp">[</span><span class="ss">mazefile</span><span class="pp">]</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./arachnid [mazefile]</code></pre>
 <h2 id="try">Try:</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">./arachnid</span> arachnid.txt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./arachnid arachnid.txt</code></pre>
 <p>and then try:</p>
-<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">./arachnid</span> arachnid.c</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./arachnid arachnid.c</code></pre>
 <p>Navigation is through the use of the <code>wasd</code> inverted-T formation on
 QWERTY keyboards. Rogue players, vi users, and Dvorak typists are
 invited to get lost (or use the alt version)!</p>
@@ -158,7 +158,7 @@ invited to get lost (or use the alt version)!</p>
 <p>If you don’t like the <code>wasd</code> movement keys you can try the vi(m) movement keys
 instead.</p>
 <h3 id="alternate-build">Alternate build:</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="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>
 <p>Use <code>arachnid.alt</code> as you would <code>arachnid</code> above.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
@@ -181,7 +181,7 @@ Another maze, <a href="arachnid.txt">arachnid.txt</a> has also been provided. Th
 255x255, about the largest maze supported, for the particularly insane maze
 explorers out there.</p>
 <h3 id="usage">Usage</h3>
-<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">./arachnid</span> <span class="pp">[</span><span class="ss">mazefile</span><span class="pp">]</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./arachnid [mazefile]</code></pre>
 <p>You can explore the maze using the <code>w</code>,<code>a</code>,<code>s</code>, and <code>d</code> keys.</p>
 <!--