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.

2006/toledo2/index.html

@@ -141,7 +141,7 @@ Location: <a href="../../location.html#MX">MX</a> - <em>United Mexican States</e
 <!-- 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>
 <p>There is <a href="#alternate-code">alternate code</a> that is based on the author’s notes
 for DOS/Windows. This cannot be tested by us, not even to compile, but it appears
 that it should be fine, after the proper header files were added.</p>
@@ -150,12 +150,12 @@ that it should be fine, after the proper header files were added.</p>
 <pre><code>    STATUS: INABIAF - please **DO NOT** fix</code></pre>
 <p>For more detailed information see <a href="../../bugs.html#2006_toledo2">2006 toledo2 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">./toledo2</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./toledo2</code></pre>
 <p>To end execution press <code>ctrl-z</code>. As mentioned in the author’s remarks and in the
 below section, it is supposed to crash on termination though some noted this
 does not seem to happen in macOS or linux in 2023.</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">./toledo2</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./toledo2</code></pre>
 <p>and then type in the following:</p>
 <pre><code>    10 PRINT &quot;HELLO WORLD!&quot;
     LIST
@@ -165,7 +165,7 @@ does not seem to happen in macOS or linux in 2023.</p>
 <p>This version, as noted, should work for DOS/Windows. It uses non-standard
 functions in place of <code>read(2)</code> and <code>write(2)</code>.</p>
 <h3 id="alternate-build">Alternate build:</h3>
-<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="fu">make</span> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <h3 id="alternate-use">Alternate use:</h3>
 <p>The author noted that for PC/DOS you will have to add <code>ANSI.SYS</code> to your
 <code>CONFIG.SYS</code> but this is also something we can’t test.</p>
@@ -203,7 +203,7 @@ the very first volume of <a href="https://en.wikipedia.org/wiki/Dr._Dobb%27s_Jou
 Journal</a>.</p>
 <p>Type using uppercase letters. Here are three example programs. Press Enter after
 each line:</p>
-<pre class="basic"><code>    10 PRINT &quot;Hello, world!&quot;
+<pre class="&lt;!---basic--&gt;"><code>    10 PRINT &quot;Hello, world!&quot;
     LIST
     RUN
 
@@ -236,7 +236,7 @@ from the <code>SOURCE</code> directory:</p>
 PIP.COM  STAT.COM  SUBMIT.COM XSUB.COM</code></pre>
 <p>To import them, you must run the emulator with an argument, by
 example:</p>
-<div class="sourceCode" id="cb9"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./toledo2</span> DDT.COM</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./toledo2 DDT.COM</code></pre>
 <p>When the <code>&gt;</code> prompt appears, do:</p>
 <pre><code>    IMPORT DDT.COM</code></pre>
 <p>When it ends, do <code>HALT</code>, so the file is closed, and you can start