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.

2020/ferguson1/COMPILING.md

@@ -33,7 +33,7 @@ I imagine that it works for 32-bit systems but I do not know for sure.
 
 You should be able to get the compiler with:
 
-```sh
+```<!---sh-->
     sudo xcode-select --install
 ```
 
@@ -53,13 +53,13 @@ you want to use the Makefile) to compile and link this entry. With Fedora more
 recent versions there's the `dnf` package manager but I cannot help with any of
 the GUI installers since I don't use them. Something like:
 
-```sh
+```<!---sh-->
     sudo dnf install ncurses-devel ncurses make gcc
 ```
 
 or
 
-```sh
+```<!---sh-->
     # dnf install ncurses-devel ncurses make gcc
 ```
 
@@ -69,25 +69,25 @@ Just like Fedora you will need `gcc`, `ncurses`, `ncurses-devel` (and if you
 want to use the Makefile `make`). CentOS uses `yum` and CentOS 8 uses `dnf`.
 So:
 
-```sh
+```<!---sh-->
     sudo yum install ncurses-devel ncurses make gcc
 ```
 
 or
 
-```sh
+```<!---sh-->
     # yum install ncurses-devel ncurses make gcc
 ```
 
 or
 
-```sh
+```<!---sh-->
     sudo dnf install ncurses-devel ncurses make gcc
 ```
 
 or
 
-```sh
+```<!---sh-->
     # dnf install ncurses-devel ncurses make gcc
 ```