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/mills2/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
@@ -18,14 +18,14 @@ For more detailed information see [2015 mills2 bugs](../../bugs.html#2015_mills2
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog compressed_file.Z
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -39,7 +39,7 @@ for a `compress(1)`-like compressor using a similar idea.
 
 Why is the sad smiley on line 12 in that particular place?
 
-```c
+```<!---c-->
     c=0)			    :( O
 ```
 
@@ -66,7 +66,7 @@ on the command line.  On the odd chance you don't have `compress(1)` hanging abo
 on your system, I've provided compressed copies of this year's IOCCC rules
 and guidelines files.  To print them, just do
 
-```sh
+```<!---sh-->
     ./prog ioccc_guidelines.txt.Z
     ./prog ioccc_rules.txt.Z
 ```

2015/mills2/index.html

@@ -141,22 +141,22 @@ 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></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make</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#2015_mills2">2015 mills2 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">./prog</span> compressed_file.Z</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog compressed_file.Z</code></pre>
 <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>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>Without ASCII art, the source code of this entry would have been exactly 256
 bytes. Compared to <a href="../../years.html#1990_jaw">1990/jaw</a>, it is very
 impressive, even taking into account the missing <code>atob</code> functionality. Now we wish
 for a <code>compress(1)</code>-like compressor using a similar idea.</p>
 <p>Why is the sad smiley on line 12 in that particular place?</p>
-<div class="sourceCode" id="cb5"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a>    c<span class="op">=</span><span class="dv">0</span><span class="op">)</span>                            <span class="op">:(</span> O</span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    c=0)                            :( O</code></pre>
 <h2 id="authors-remarks">Author’s remarks:</h2>
 <h3 id="the-program">The Program</h3>
 <p>This program is an implementation of the unix <code>zcat(1)</code> command for printing
@@ -174,8 +174,8 @@ single function and a few <code>int</code>s.</p>
 on the command line. On the odd chance you don’t have <code>compress(1)</code> hanging about
 on your system, I’ve provided compressed copies of this year’s IOCCC rules
 and guidelines files. To print them, just do</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> ioccc_guidelines.txt.Z</span>
-<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./prog</span> ioccc_rules.txt.Z</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./prog ioccc_guidelines.txt.Z
+    ./prog ioccc_rules.txt.Z</code></pre>
 <h3 id="the-details">The Details</h3>
 <p>The basic cleverness here comes from realizing that the compressed data is
 itself an encoded version of the code dictionary. When the encoder sees