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.

1991/buzzard/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
@@ -21,7 +21,7 @@ For more detailed information see [1991 buzzard bugs](../../bugs.html#1991_buzza
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./buzzard
 ```
 
@@ -37,14 +37,14 @@ code directly so the keys are not made a `-D` at the compiler.
 
 ### Alternate build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
 
 ### Alternate use:
 
-```sh
+```<!---sh-->
     ./buzzard.alt
 ```
 
@@ -89,7 +89,7 @@ so make sure to convert tabs to spaces before using it.
 
 Usage:
 
-```sh
+```<!---sh-->
     ./buzzard [filename [escape-char [start-x start-yNNN
 ```
 

1991/buzzard/index.html

@@ -141,7 +141,7 @@ Location: <a href="../../location.html#ZZ">ZZ</a> - <em>Unknown location</em></l
 <!-- 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>
 <p>There is an <a href="#alternate-code">alternate version</a> which might feel more at home
 for vi(m) users in navigation.</p>
 <h3 id="bugs-and-misfeatures">Bugs and (Mis)features:</h3>
@@ -149,7 +149,7 @@ for vi(m) users in navigation.</p>
 <pre><code>    STATUS: INABIAF - please **DO NOT** fix</code></pre>
 <p>For more detailed information see <a href="../../bugs.html#1991_buzzard">1991 buzzard 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">./buzzard</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./buzzard</code></pre>
 <h2 id="alternate-code">Alternate code:</h2>
 <p>This version changes the keys <code>f</code> for forward, <code>l</code> for left and <code>r</code> for right by
 default to <code>k</code> for forward, <code>l</code> for right and <code>h</code> for left, which is more
@@ -157,9 +157,9 @@ natural for those who use vi(m). Also one can just hit <code>q</code> followed b
 quit the maze. It is problematic to reconfigure the keys except by modifying the
 code directly so the keys are not made a <code>-D</code> at the compiler.</p>
 <h3 id="alternate-build">Alternate build:</h3>
-<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">make</span> alt</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make alt</code></pre>
 <h3 id="alternate-use">Alternate use:</h3>
-<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">./buzzard.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./buzzard.alt</code></pre>
 <h2 id="judges-remarks">Judges’ remarks:</h2>
 <p>You will be A-mazed.</p>
 <p>You are invited to try to cheat, … if you can figure out how! :-)</p>
@@ -186,7 +186,7 @@ separate physical rows in the maze; a space indicates a corridor,
 and any other character is a wall. Tabs are also considered walls,
 so make sure to convert tabs to spaces before using it.</p>
 <p>Usage:</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">./buzzard</span> [filename [escape-char [start-x start-yNNN</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./buzzard [filename [escape-char [start-x start-yNNN</code></pre>
 <p>Filename is the name of the file containing the maze. This
 defaults to <code>buzzard.c</code> or rather <code>__FILE__</code>.</p>
 <p>Escape-char is the character in the maze that represents the exit.