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.

2005/vik/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./vik [file.map]
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./vik maze.map
 ```
 
@@ -60,7 +60,7 @@ Compile the source code and link in [X
 libraries](https://en.wikipedia.org/wiki/Xlib) if necessary. The program takes
 three options which have to be typed in a specific order as described below.
 
-```sh
+```<!---sh-->
     ./vik [-w <width>] [mapfile]
 ```
 
@@ -75,20 +75,20 @@ where:
 
 Start the engine using a built in labyrinth and texture bitmaps:
 
-```sh
+```<!---sh-->
     ./vik
 ```
 
 Start the engine and loads the labyrinth defined in the file
 [maze.map](maze.map):
 
-```sh
+```<!---sh-->
     ./vik maze.map
 ```
 
 Start the engine using [maze.map](maze.map) in a window that is 400 pixels wide:
 
-```sh
+```<!---sh-->
     ./vik -w 400 maze.map
 ```