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/persano/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
@@ -10,14 +10,14 @@ setting binary mode on `stdout`. See [alternate code](#alternate-code) below.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./persano p q [num frames]
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./try.sh
 ```
 
@@ -49,7 +49,7 @@ Use `persano.alt` as you would `persano` above.
 
 ### Alternate try:
 
-```sh
+```<!---sh-->
     ./persano.alt 3 16 > knot3-16.gif
 ```
 
@@ -80,7 +80,7 @@ knots](https://en.wikipedia.org/wiki/Torus_knot) to standard output.
 
 ### SYNOPSIS
 
-```sh
+```<!---sh-->
     ./persano p q [num frames]
 ```
 
@@ -98,14 +98,14 @@ cutting it [^1], until it ends up looking just like a circle embedded in R3 [^2]
 
 Sample usage:
 
-```sh
+```<!---sh-->
     ./persano 3 2 1 > foo.gif
 ```
 
 writes a non-animated GIF (a single frame) stream of a rendered trefoil
 knot to the file `foo.gif`.
 
-```sh
+```<!---sh-->
     ./persano 5 2
 ```