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/jaw/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
@@ -9,7 +9,7 @@
 
 To test the official C entry, one might try:
 
-```sh
+```<!---sh-->
     echo "Quartz glyph jocks vend, fix, BMW." | compress | ./btoa | ./jaw
 ```
 
@@ -19,7 +19,7 @@ sentence.
 
 #### Also try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -39,14 +39,14 @@ it to 1530 bytes) which implements the complete shark utility. The script,
 The sender must have `compress` and `btoa`. To send, try:
 
 
-```sh
+```<!---sh-->
     ./shark.sh jaw.* README.md > receive
 ```
 
 The resulting file, `receive`, unpacks the input files
 even if the receiver lacks `uncompress` and `btoa`:
 
-```sh
+```<!---sh-->
     mkdir -p test
     cd test
     sh ../receive
@@ -168,7 +168,7 @@ Construct `sharkmail`, to auto-split `sharkives` into mailable segments and mail
 them. Here's a simple one, which could be extended to enable auto-reassembly
 with one shell cmd at the far end.
 
-```sh
+```<!---sh-->
     #!/bin/sh
     m=$1; shift
     shark $* | split -800 - /tmp/shark$$