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.

2018/endoh1/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog < textfile > output.gif
 ```
 
@@ -16,7 +16,7 @@
 
 To see the input files and feed them to the program, redirecting to GIF files:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -40,7 +40,7 @@ least 2MiB of memory to run in.
 
 This program generates an animated GIF from a plain text.  Run:
 
-```sh
+```<!---sh-->
     cc -o prog prog.c
     ./prog < invisible.txt > invisible.gif
 ```
@@ -51,14 +51,14 @@ letters that leave the mark and ones that do not?
 
 Other examples:
 
-```sh
+```<!---sh-->
     ./prog < golem.txt > golem.gif
     ./prog < smily.txt > smily.gif
 ```
 
 The program itself has a hidden message.
 
-```sh
+```<!---sh-->
     ./prog < prog.c > prog.gif
 ```
 

2018/endoh1/index.html

@@ -141,12 +141,12 @@ 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 class="op">&lt;</span> textfile <span class="op">&gt;</span> output.gif</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog &lt; textfile &gt; output.gif</code></pre>
 <h2 id="try">Try:</h2>
 <p>To see the input files and feed them to the program, redirecting to GIF files:</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>To get the best experience, use a GIF viewer that can handle animated GIFs.
 With macOS you can use Safari using <code>open -a Safari smily.gif</code>.</p>
@@ -158,16 +158,16 @@ how does it know which characters are closed?</p>
 least 2MiB of memory to run in.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <p>This program generates an animated GIF from a plain text. 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">cc</span> <span class="at">-o</span> prog prog.c</span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span> <span class="op">&lt;</span> invisible.txt <span class="op">&gt;</span> invisible.gif</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    cc -o prog prog.c
+    ./prog &lt; invisible.txt &gt; invisible.gif</code></pre>
 <p>Open <code>invisible.gif</code> with a GIF viewer that can show animated GIFs and then wait
 a minute. You will see a hidden message. Can you tell the difference between
 letters that leave the mark and ones that do not?</p>
 <p>Other examples:</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="ex">./prog</span> <span class="op">&lt;</span> golem.txt <span class="op">&gt;</span> golem.gif</span>
-<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span> <span class="op">&lt;</span> smily.txt <span class="op">&gt;</span> smily.gif</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog &lt; golem.txt &gt; golem.gif
+    ./prog &lt; smily.txt &gt; smily.gif</code></pre>
 <p>The program itself has a hidden message.</p>
-<div class="sourceCode" id="cb6"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span> <span class="op">&lt;</span> prog.c <span class="op">&gt;</span> prog.gif</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog &lt; prog.c &gt; prog.gif</code></pre>
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