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.

1998/banks/README.md

@@ -1,6 +1,6 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make all
 ```
 
@@ -34,14 +34,14 @@ macros to, depending on what controls you wish to redefine. For instance, to set
 the throttle up and down to `u` and `d`:
 
 
-```sh
+```<!---sh-->
     make clobber IT=XK_u DT=XK_d all
 ```
 
 because in the header file you can see that `XK_u` corresponds to `u` and `XK_d`
 corresponds to `d`:
 
-```c
+```<!---c-->
     #define XK_d                             0x0064  /* U+0064 LATIN SMALL LETTER D */
     #define XK_u                             0x0075  /* U+0075 LATIN SMALL LETTER U */
 ```
@@ -63,7 +63,7 @@ preselected alternative keys.
 
 ## To use:
 
-```sh
+```<!---sh-->
     cat horizon.sc pittsburgh.sc | ./banks
 ```
 
@@ -106,7 +106,7 @@ the right side for movement. These are hard coded, as noted.
 
 To use the default settings for the alternate build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
@@ -231,7 +231,7 @@ Here is a brief description of the scenery files:
 
 A few examples of how to input scenery:
 
-```sh
+```<!---sh-->
     cat horizon.sc pittsburgh.sc | ./banks
     cat mountains.sc bb.sc | ./banks
     cat mountains.sc river.sc pyramids.sc | ./banks
@@ -240,7 +240,7 @@ A few examples of how to input scenery:
 You can simulate flying through a cloud bank as well:
 
 
-```sh
+```<!---sh-->
     ./banks < /dev/null
 ```