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/rcm/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./rcm < file.gz
 ```
 
@@ -18,7 +18,7 @@ where `file.gz` is some gzipped file.
 
 For more information try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -27,7 +27,7 @@ For more information try:
 
 For a good no-op try:
 
-```sh
+```<!---sh-->
     gzip -c < rcm.c | ./rcm
 ```
 

1996/rcm/index.html

@@ -141,16 +141,16 @@ 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> 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">./rcm</span> <span class="op">&lt;</span> file.gz</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./rcm &lt; file.gz</code></pre>
 <p>where <code>file.gz</code> is some gzipped file.</p>
 <h2 id="try">Try:</h2>
 <p>For more information 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="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>For a good no-op 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="fu">gzip</span> <span class="at">-c</span> <span class="op">&lt;</span> rcm.c <span class="kw">|</span> <span class="ex">./rcm</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    gzip -c &lt; rcm.c | ./rcm</code></pre>
 <p>NOTE: this is done in the <a href="try.sh">try.sh</a> script as well, along with some other
 commands including a way to do the above command but with more steps.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>