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.

2013/hou/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
@@ -18,7 +18,7 @@ For more detailed information see [2013 hou bugs](../../bugs.html#2013_hou).
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./hou [scene-file-name] [options]
 ```
 
@@ -29,7 +29,7 @@ effects should be more or less recognizable when you see 16.
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -62,7 +62,7 @@ This program will loop infinitely while progressively refining a
 NOTE: the author refers to [a.c](a.c), placed in a gzipped file `a.c.gz`. We do not
 include it but it can be generated like:
 
-```sh
+```<!---sh-->
     cc -Wall hou.c -o hou -lm
     ./hou > a.c
 ```
@@ -78,7 +78,7 @@ needing to create a temporary file.
 This program is a programmable rendering engine with a built-in default scene.
 The standard command line is:
 
-```sh
+```<!---sh-->
     ./hou [scene-file-name] [options]
 ```
 

2013/hou/index.html

@@ -141,18 +141,18 @@ Location: <a href="../../location.html#CN">CN</a> - <em>People’s Republic of C
 <!-- 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>
 <h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
 <p>The current status of this entry is:</p>
 <pre><code>    STATUS: INABIAF - please **DO NOT** fix</code></pre>
 <p>For more detailed information see <a href="../../bugs.html#2013_hou">2013 hou bugs</a>.</p>
 <h2 id="to-use">To use:</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">./hou</span> <span class="pp">[</span><span class="ss">scene</span><span class="pp">-</span><span class="ss">file</span><span class="pp">-</span><span class="ss">name</span><span class="pp">]</span> <span class="pp">[</span><span class="ss">options</span><span class="pp">]</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./hou [scene-file-name] [options]</code></pre>
 <p>Follow the instructions in <code>stdout</code>, preferably with an auto-refreshing PPM
 image viewer ready. Refresh the image every time the output refreshes, all
 effects should be more or less recognizable when you see 16.</p>
 <h2 id="try">Try:</h2>
-<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">./try.sh</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./try.sh</code></pre>
 <p>Try opening the file noted by the program then let the program run a while and
 every so often reopen the file, to see how it changes. The author suggests that
 you leave the program running overnight to see what happens. If however you do
@@ -181,15 +181,15 @@ program.</p>
 <a href="https://en.wikipedia.org/wiki/Ray_tracing_(graphics)">raytraced</a> image.</p>
 <p>NOTE: the author refers to <a href="a.c">a.c</a>, placed in a gzipped file <code>a.c.gz</code>. We do not
 include it but it can be generated like:</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">-Wall</span> hou.c <span class="at">-o</span> hou <span class="at">-lm</span></span>
-<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./hou</span> <span class="op">&gt;</span> a.c</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    cc -Wall hou.c -o hou -lm
+    ./hou &gt; a.c</code></pre>
 <p>but there is no need to do this as the Makefile takes care of it without even
 needing to create a temporary file.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="using-hou">Using hou</h3>
 <p>This program is a programmable rendering engine with a built-in default scene.
 The standard command line is:</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">./hou</span> <span class="pp">[</span><span class="ss">scene</span><span class="pp">-</span><span class="ss">file</span><span class="pp">-</span><span class="ss">name</span><span class="pp">]</span> <span class="pp">[</span><span class="ss">options</span><span class="pp">]</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./hou [scene-file-name] [options]</code></pre>
 <p>As <code>hou</code> runs, it writes a progressively refining image to a ppm file specified
 in the scene. The initialization may take a while, but once it’s done, a rough
 preview should be available in seconds. Leave <code>hou</code> running for the night, and you