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.

1998/schweikh1/macos.html

@@ -138,7 +138,7 @@ a file was not found (this limitation was removed in both versions in 2023). see
 <p>However, as noted, macOS does <strong>not</strong> have <code>/usr/include</code> so this would never
 work for macOS without some changes, described next. For macOS you will need the
 command line tools installed which can be done like:</p>
-<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">sudo</span> xcode-select <span class="at">--install</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    sudo xcode-select --install</code></pre>
 <p>An important point is that the original version hard-coded <code>gcc</code> but just like
 the entry, the alternate version has also removed this limitation despite <code>gcc</code>
 existing (though it’s <code>clang</code>) in macOS.</p>
@@ -154,9 +154,9 @@ the command is:</p>
 <p>which has been changed to be:</p>
 <pre><code>&quot;0cc -ansi -E -dM -undef %s /usr/include/%s&gt;r\0 (&quot;</code></pre>
 <p>Shortly below that you will see, as noted above, the numbers:</p>
-<div class="sourceCode" id="cb4"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>    <span class="cf">if</span> <span class="op">((</span>H <span class="op">=</span> fopen <span class="op">(</span>__FILE__<span class="op">+</span><span class="dv">43</span><span class="op">,</span> <span class="dv">43</span><span class="op">+</span>__FILE__<span class="op">)))</span></span>
-<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a>    <span class="cf">while</span> <span class="op">((</span>fgets <span class="op">(</span>L<span class="op">,</span> <span class="op">(</span><span class="dt">int</span><span class="op">)</span><span class="kw">sizeof</span> L<span class="op">,</span> H<span class="op">))</span> <span class="op">!=</span> <span class="dv">0</span><span class="op">)</span> <span class="op">{</span></span>
-<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a>            I<span class="op">[</span>strcspn <span class="op">(</span>I<span class="op">,</span> <span class="dv">45</span><span class="op">+</span>__FILE__<span class="op">)]</span> <span class="op">=</span> O <span class="op">=</span> <span class="dv">0</span><span class="op">;</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    if ((H = fopen (__FILE__+43, 43+__FILE__)))
+    while ((fgets (L, (int)sizeof L, H)) != 0) {
+            I[strcspn (I, 45+__FILE__)] = O = 0;</code></pre>
 <p>The first number in the above C means the length starting from 0 up through the
 <code>&gt;</code>. The second number is the same starting point but up through the <code>\0</code> which
 is why it’s <code>+2</code>. But what happens if only the first number is updated (from the