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.

2011/toledo/README.md

@@ -2,7 +2,7 @@
 
 If you have X11 installed:
 
-```sh
+```<!---sh-->
     make
 ```
 
@@ -13,7 +13,7 @@ Windows](toledo.alt2.c). See [Alternate code](#alternate-code) below.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./toledo
 ```
 
@@ -49,7 +49,7 @@ but you can change them about however you like, even with other keys. For
 instance to swap `LEFT` and `RIGHT`:
 
 
-```sh
+```<!---sh-->
     make clobber LEFT=XK_Right:XK_d RIGHT=XK_Left:XK_a alt
 ```
 
@@ -75,7 +75,7 @@ the source early on, right before the code gets hard to follow, or using the
 Like Oscar's previous winning X11 program for the 19th IOCCC, if
 you remove both the X11 include files and replace them with
 
-```c
+```<!---c-->
     #include "layer.c"
 ```