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.

2020/endoh2/README.md

@@ -1,26 +1,26 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
 What happens if you do
 
-```sh
+```<!---sh-->
     ./prog prog.c
 ```
 
@@ -41,7 +41,7 @@ render for a larger terminal window?  How about adding more glyphs?
 
 No!  Try not.  Do, or do not.  There is no try.
 
-```sh
+```<!---sh-->
     cc -std=c99 prog.c
     ./a.out
     ./a.out hello.txt

2020/endoh2/index.html

@@ -141,13 +141,13 @@ 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>
-<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>What happens if you do</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">./prog</span> prog.c</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog prog.c</code></pre>
 <p>?</p>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Clever use of the C99 complex data type. The <a href="spoiler/">spoiler</a> directory
@@ -157,11 +157,11 @@ shapes.</p>
 render for a larger terminal window? How about adding more glyphs?</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <p>No! Try not. Do, or do not. There is no try.</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">cc</span> <span class="at">-std</span><span class="op">=</span>c99 prog.c</span>
-<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span></span>
-<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span> hello.txt</span>
-<span id="cb5-4"><a href="#cb5-4" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span> yoda.txt</span>
-<span id="cb5-5"><a href="#cb5-5" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./a.out</span> bear.txt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    cc -std=c99 prog.c
+    ./a.out
+    ./a.out hello.txt
+    ./a.out yoda.txt
+    ./a.out bear.txt</code></pre>
 <p>See spoiler.zip for the source code.
 <a href="https://en.wikipedia.org/wiki/List_of_the_most_common_passwords">The 16th most common password on the Internet in 2017 (according to Splash Data)</a> the password is.</p>
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