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.

1986/marshall/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
@@ -18,7 +18,7 @@ if nothing else.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./marshall
 ```
 
@@ -36,14 +36,14 @@ instead offer the problematic code as an alternate version whereas
 To see if your compiler has the problems noted:
 
 
-```sh
+```<!---sh-->
     make alt
 ```
 
 
 ### Alternate use:
 
-```sh
+```<!---sh-->
     ./marshall.alt
 ```
 

1986/marshall/compilers.html

@@ -162,7 +162,7 @@ because of the call to <code>_exit()</code> (see below).</p>
 enable the optimiser clang will generate code that prints the string twice and
 dumps core just like before! What about the call to <code>_exit()</code>?</p>
 <p>The call was:</p>
-<div class="sourceCode" id="cb1"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a>    _exit<span class="op">(</span>argv<span class="op">[(</span><span class="dt">int</span><span class="op">)*</span>argc<span class="op">-</span><span class="dv">2</span><span class="op">/</span>cc<span class="op">[</span><span class="dv">1</span><span class="op">*(</span><span class="dt">int</span><span class="op">)*</span>argc<span class="op">]|-</span><span class="dv">1</span><span class="op">&lt;&lt;</span><span class="dv">4</span><span class="op">]);</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    _exit(argv[(int)*argc-2/cc[1*(int)*argc]|-1&lt;&lt;4]);</code></pre>
 <p>Changing it to not refer to these variables and just exit 1 and the problems
 disappear!</p>
 <h3 id="macos">macOS</h3>
@@ -172,9 +172,9 @@ it works fine but if it’s disabled it prints out the string and then enters an
 infinite loop!</p>
 <p>After we fix the infinite loop if we change the <code>_exit()</code> call in macOS and
 disable the optimiser we might get something like:</p>
-<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">$</span> ./marshall</span>
-<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>          <span class="ex">choo</span> choo</span>
-<span id="cb2-3"><a href="#cb2-3" aria-hidden="true" tabindex="-1"></a>    <span class="ex">Segmentation</span> fault: 11</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    $ ./marshall
+          choo choo
+    Segmentation fault: 11</code></pre>
 <p>Observe how it doesn’t print it twice. But of course it segfaults so it’s not
 right either.</p>
 <p>If the optimiser is enabled, however, we will see that it works fine before the

1986/marshall/compilers.md

@@ -54,7 +54,7 @@ dumps core just like before!  What about the call to `_exit()`?
 The call was:
 
 
-```c
+```<!---c-->
     _exit(argv[(int)*argc-2/cc[1*(int)*argc]|-1<<4]);
 ```
 
@@ -72,7 +72,7 @@ infinite loop!
 After we fix the infinite loop if we change the `_exit()` call in macOS and
 disable the optimiser we might get something like:
 
-```sh
+```<!---sh-->
     $ ./marshall
 	  choo choo
     Segmentation fault: 11

1986/marshall/index.html

@@ -141,7 +141,7 @@ 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> all</span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    make all</code></pre>
 <p>NOTE: we FORCE disable the optimiser due to a funny problem with different
 compilers and systems. See below and <a href="compilers.html">compilers.html</a> for details.</p>
 <p>There is an <a href="#alternate-code">alternate version</a>. The reason is a funny problem:
@@ -152,7 +152,7 @@ might work but the other one would not. We describe this in more detail in
 <a href="compilers.html">compilers.html</a> and we encourage you to read it for entertainment
 if nothing else.</p>
 <h2 id="to-use">To use:</h2>
-<div class="sourceCode" id="cb2"><pre class="sourceCode sh"><code class="sourceCode bash"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>    <span class="ex">./marshall</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./marshall</code></pre>
 <h2 id="alternate-code">Alternate code:</h2>
 <p>Due to the different <a href="compilers.html">conflicting problems</a> with gcc and clang, we
 instead offer the problematic code as an alternate version whereas
@@ -160,9 +160,9 @@ instead offer the problematic code as an alternate version whereas
 <code>_exit()</code> commented out, changing the value passed into <code>_exit()</code> to <code>1</code>.</p>
 <h3 id="alternate-build">Alternate build:</h3>
 <p>To see if your compiler has the problems noted:</p>
-<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="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="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">./marshall.alt</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    ./marshall.alt</code></pre>
 <p>Does it work in your system? That is does it not segfault, does it print it only
 once and does it not enter an infinite loop? Or more generally does it print the
 text exactly once and then exit?</p>