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.

2015/endoh3/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog
 ```
 
@@ -16,7 +16,7 @@
 
 To see the original [mullender](mullender.c) in action:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -26,7 +26,7 @@ like at the end. Send INTR to end the program.
 
 More generally use:
 
-```sh
+```<!---sh-->
     cc -o prog prog.c foo.c
     ./prog
     ^C	# if necessary, where ^C is ctrl-C, interrrupt
@@ -71,7 +71,7 @@ Read it upside down.)
 
 You got it?  This program is supposed to be used in this way:
 
-```sh
+```<!---sh-->
     wget https://www.ioccc.org/1984/mullender.c
     clang -o prog prog.c mullender.c
     ./prog

2015/endoh3/index.html

@@ -141,19 +141,19 @@ Location: <a href="../../location.html#JP">JP</a> - <em>Japan</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>
 <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">./prog</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog</code></pre>
 <h2 id="try">Try:</h2>
 <p>To see the original <a href="mullender.c">mullender</a> in action:</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>
 <p>Observe what happens when you hit enter or another character! You might even try
 typing out, one character at a time, <code>1984/mullender</code>, and then see what it looks
 like at the end. Send INTR to end the program.</p>
 <p>More generally use:</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">cc</span> <span class="at">-o</span> prog prog.c foo.c</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span></span>
-<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a>    <span class="ex">^C</span>  <span class="co"># if necessary, where ^C is ctrl-C, interrrupt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    cc -o prog prog.c foo.c
+    ./prog
+    ^C  # if necessary, where ^C is ctrl-C, interrrupt</code></pre>
 <p>to compile and run <code>prog</code> as whatever foo.c is in the joke PDP-11 emulator.</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Like <a href="https://en.wikipedia.org/wiki/Marty_McFly">Marty</a> and
@@ -181,9 +181,9 @@ the source code from all angles..</li>
 <p>This program is a joke PDP-11 emulator. (“ll-dpd” is embedded in the code.
 Read it upside down.)</p>
 <p>You got it? This program is supposed to be used in this way:</p>
-<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">wget</span> https://www.ioccc.org/1984/mullender.c</span>
-<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a>    <span class="fu">clang</span> <span class="at">-o</span> prog prog.c mullender.c</span>
-<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    wget https://www.ioccc.org/1984/mullender.c
+    clang -o prog prog.c mullender.c
+    ./prog</code></pre>
 <p>You can enjoy the legendary winning entry of the first IOCCC, again.</p>
 <h3 id="internal">Internal</h3>
 <p>This program uses <code>__attribute__((constructor))</code>, which is a GCC extension, to