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.

1996/eldby/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
@@ -11,7 +11,7 @@ section.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./eldby.alt
 ```
 
@@ -28,7 +28,7 @@ problematic for some people, can be configured to different speeds by way of the
 value used in `usleep()`. The default is `35000` but you can easily change
 it. To do so try:
 
-```sh
+```<!---sh-->
     make SLEEP=20000 clobber alt
     ./eldby.alt
 ```
@@ -41,7 +41,7 @@ This version is the original which has no sleep time in between updates.
 
 ### Original build:
 
-```sh
+```<!---sh-->
     make all
 ```
 

1996/eldby/index.html

@@ -141,12 +141,12 @@ Location: <a href="../../location.html#ZZ">ZZ</a> - <em>Unknown location</em></l
 <!-- 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> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <p>We recommend that you use the alt version to see what the entry looked like back
 in 1996. For the original version see the <a href="#original-code">original code</a>
 section.</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">./eldby.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./eldby.alt</code></pre>
 <p>To quit send intr (typically ctrl-c).</p>
 <p>NOTE: to reset the sanity of your terminal after this program ends try <code>reset</code>.</p>
 <h2 id="try">Try:</h2>
@@ -155,12 +155,12 @@ happening with modern systems, and to not flash too quickly, which can be
 problematic for some people, can be configured to different speeds by way of the
 value used in <code>usleep()</code>. The default is <code>35000</code> but you can easily change
 it. To do so try:</p>
-<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="fu">make</span> SLEEP=20000 clobber alt</span>
-<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./eldby.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make SLEEP=20000 clobber alt
+    ./eldby.alt</code></pre>
 <h2 id="original-code">Original code:</h2>
 <p>This version is the original which has no sleep time in between updates.</p>
 <h3 id="original-build">Original 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> all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make all</code></pre>
 <h3 id="original-use">Original use:</h3>
 <p>Use <code>./eldby</code> as you would <code>./eldby.alt</code> above.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>