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.

1995/garry/README.md

@@ -1,20 +1,20 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./garry <input_file >output_file
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -29,21 +29,21 @@ left intact) looked very much like a rat "dropping core".  See
 
 ### Alternate build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
 
 ### Alternate use:
 
-```sh
+```<!---sh-->
     ./garry.alt <input_file >output_file
 ```
 
 
 ### Alternate try:
 
-```sh
+```<!---sh-->
     ./try.alt.sh
 ```
 
@@ -63,13 +63,13 @@ environment variables.
 The calling syntax is pretty simple, just use it with `stdio`-redirection
 or inside pipelines, e.g.:
 
-```sh
+```<!---sh-->
     ./garry <file_to_convert >converted_file
 ```
 
 or
 
-```sh
+```<!---sh-->
     cat all_my_files/* | ./garry | lp
 ```
 
@@ -87,7 +87,7 @@ Unknown Env-variables or malformed expressions are ignored and kept intact.
 Additionally, the filter replaces escaped octal values in the environment
 variables by their binary representation, e.g.:
 
-```sh
+```<!---sh-->
     $ TEST="\110\145\154\154\157"
     $ export TEST
     $ echo '$TEST$' | ./garry