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.

1990/dg/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     echo foo bar | ./dg
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -24,13 +24,13 @@
 Some C preprocessors got confused about single quotes in certain cases.
 In particular, the following source line:
 
-```c
+```<!---c-->
     b12(ase(bco(acp(bi(acp(bcp(acp(bpl(aqu(bqu(A))))))))))))))))))))))))))))))
 ```
 
 sometimes has to be changed to:
 
-```c
+```<!---c-->
     b12(ase(bco(acp(bi(acp(bcp(acp(bpl('A'))))))))))))))))))))))))))))
 ```
 
@@ -56,7 +56,7 @@ As for the rot13 algorithm, it relies on `index(3)` to find if the
 character is in the set `A-Za-z`. `l[]` is an array that gets filled
 with:
 
-```c
+```<!---c-->
     "nopqrstuvwxyzzzzabcdefghijklmmmmNOPQRSTUVWXYZZZZABCDEFGHIJKLMMMM"
 ```
 

1990/dg/index.html

@@ -141,17 +141,17 @@ 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>
 <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="bu">echo</span> foo bar <span class="kw">|</span> <span class="ex">./dg</span></span></code></pre></div>
+<pre class="&lt;!---sh--&gt;"><code>    echo foo bar | ./dg</code></pre>
 <h2 id="try">Try:</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">./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>Some C preprocessors got confused about single quotes in certain cases.
 In particular, the following source line:</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>    b12<span class="op">(</span>ase<span class="op">(</span>bco<span class="op">(</span>acp<span class="op">(</span>bi<span class="op">(</span>acp<span class="op">(</span>bcp<span class="op">(</span>acp<span class="op">(</span>bpl<span class="op">(</span>aqu<span class="op">(</span>bqu<span class="op">(</span>A<span class="op">))))))))))))))))))))))))))))))</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    b12(ase(bco(acp(bi(acp(bcp(acp(bpl(aqu(bqu(A))))))))))))))))))))))))))))))</code></pre>
 <p>sometimes has to be changed to:</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>    b12<span class="op">(</span>ase<span class="op">(</span>bco<span class="op">(</span>acp<span class="op">(</span>bi<span class="op">(</span>acp<span class="op">(</span>bcp<span class="op">(</span>acp<span class="op">(</span>bpl<span class="op">(</span><span class="ch">&#39;A&#39;</span><span class="op">))))))))))))))))))))))))))))</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    b12(ase(bco(acp(bi(acp(bcp(acp(bpl(&#39;A&#39;))))))))))))))))))))))))))))</code></pre>
 <p>particularly if the C preprocessor botches single quotes in cpp expansions,
 which we have done for the wider audience.</p>
 <h2 id="authors-remarks">Author’s remarks:</h2>
@@ -167,7 +167,7 @@ source. The <code>axx()</code> <code>#define</code>s do the same, but add tokens
 <p>As for the rot13 algorithm, it relies on <code>index(3)</code> to find if the
 character is in the set <code>A-Za-z</code>. <code>l[]</code> is an array that gets filled
 with:</p>
-<div class="sourceCode" id="cb6"><pre class="sourceCode c"><code class="sourceCode c"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>    <span class="st">&quot;nopqrstuvwxyzzzzabcdefghijklmmmmNOPQRSTUVWXYZZZZABCDEFGHIJKLMMMM&quot;</span></span></code></pre></div>
+<pre class="&lt;!---c--&gt;"><code>    &quot;nopqrstuvwxyzzzzabcdefghijklmmmmNOPQRSTUVWXYZZZZABCDEFGHIJKLMMMM&quot;</code></pre>
 <p>If <code>index(3)</code> says the char is in the alphabet, then XOR the offset
 with <code>16</code> to translate, and output, otherwise pass it unchanged.</p>
 <!--