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.

2015/dogon/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```sh
+```<!---sh-->
     make
 ```
 
 To change the dimensions you can use the `WIDTH` and `HEIGHT` variables when
 compiling (default 1024 x 800):
 
-```sh
+```<!---sh-->
     make clobber WIDTH=640 HEIGHT=480
 ```
 
@@ -22,14 +22,14 @@ code](#alternate-code) below.
 
 ## To use:
 
-```sh
+```<!---sh-->
     ./prog
 ```
 
 
 ## Try:
 
-```sh
+```<!---sh-->
     ./prog
 ```
 
@@ -77,7 +77,7 @@ This alt version does this for you.
 
 ### Alternate build:
 
-```sh
+```<!---sh-->
     make alt
 ```
 
@@ -174,7 +174,7 @@ important support of up to 32 function keys keyboards without spilling over the
 size limit, and allows us to use such fun expression for arrow view control as
 the following:
 
-```c
+```<!---c-->
     *(a&1?&C:&B)-=(.05 -a/2%2*.1)*!(a-1&4092^3920)
 ```