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.

1992/nathan/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./nathan
     # enter some text
 ```
@@ -17,7 +17,7 @@
 
 To see some other fun uses:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -58,7 +58,7 @@ distribute some winning entries outside of the US.
 Nathan Sidwell stated that he was willing to distribute the winning source.  To
 read HIS instructions of how to obtain his winning program one was able to run:
 
-```sh
+```<!---sh-->
     make nathan
     ./nathan
 ```

1992/nathan/index.html

@@ -141,13 +141,13 @@ Location: <a href="../../location.html#GB">GB</a> - <em>United Kingdom of Great
 <!-- 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> all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make all</code></pre>
 <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">./nathan</span></span>
-<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>    <span class="co"># enter some text</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./nathan
+    # enter some text</code></pre>
 <h2 id="try">Try:</h2>
 <p>To see some other fun uses:</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="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>
 <h3 id="warning">WARNING:</h3>
 <p>The judges make no claim as to the strength or security
@@ -173,8 +173,8 @@ fall under this restricted category, the judges originally were not able to
 distribute some winning entries outside of the US.</p>
 <p>Nathan Sidwell stated that he was willing to distribute the winning source. To
 read HIS instructions of how to obtain his winning program one was able to run:</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="fu">make</span> nathan</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./nathan</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make nathan
+    ./nathan</code></pre>
 <p>to learn how to get a copy of the code.</p>
 <p>See the 1992/nathan.c file in the
 <a href="../../archive/historic/archive-1992.tar.bz2">archive/historic/archive-1992.tar.bz2</a>