improve how markdown code language is commented

We added a space between the markdown triple code mark
and language that was enclosed in HTML comments.

So a line of the form:

````
```<!---c--->
````

became:

````
``` <!---c--->
````

This was done to **help** some code see that the HTML comment
string was not a markdown code specifier.   Not all code
understands this after this changed.  For example, `pandoc(1)`
still forms HTML classes of the form "&lt;!---c--&gt;"
when it encounters the above mentioned change.

We also fixed a problem with `2019/dogon/README.md` regarding
a markdown code block.

We also fixed a problem with `2020/yang/README.md` regarding
a markdown code block.

1992/kivinen/README.md

@@ -2,7 +2,7 @@
 
 If your machine support the X Window System, Version 11:
 
-```<!---sh-->
+``` <!---sh-->
     make alt
 ```
 
@@ -24,7 +24,7 @@ For more detailed information see [1992 kivinen bugs](../../bugs.html#1992_kivin
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     ./kivinen.alt
 
     ./kivinen.alt a
@@ -41,7 +41,7 @@ Also try changing the speed that the game moves. For instance if you wish to
 change the `usleep(3)` value to `30000` from `20000`, try:
 
 
-```<!---sh-->
+``` <!---sh-->
     make clobber SLEEP=30000 alt # make it slower
 
     make clobber SLEEP=10000 alt # make it faster
@@ -59,7 +59,7 @@ code.
 
 ### Original build:
 
-```<!---sh-->
+``` <!---sh-->
     make all
 ```