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.

1996/schweikh2/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./schweikh2
 ```
 
@@ -24,19 +24,19 @@ The program accepts up to 4 parameters:
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
 What happens if you pass only three parameters like the below?
 
-```sh
+```<!---sh-->
     ./schweikh2 15 1 0
 ```
 
 The author also suggests:
 
-```sh
+```<!---sh-->
     while :; do grep -v '#' schweikh2.c; done
 ```
 
@@ -51,7 +51,7 @@ The original program, with only slight obfuscations, may be found
 in [hunni.c](hunni.c). The perl script, [hunni.pl](hunni.pl), obfuscates it
 appropriately. Try:
 
-```sh
+```<!---sh-->
     less hunni.c
 
     perl ./hunni.pl < hunni.c
@@ -137,7 +137,7 @@ minutes (`gcc -O3`).
 
 ### Sample arguments:
 
-```sh
+```<!---sh-->
     ./schweikh2 6
     ./schweikh2 7 0
     ./schweikh2 7 7 0
@@ -151,7 +151,7 @@ minutes (`gcc -O3`).
 The diamond pattern can be continued without a break.
 For a nice printout try this on your Bourne compatible shell:
 
-```sh
+```<!---sh-->
     while :; do grep -v '#' schweikh2.c; done
 ```