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.

1998/dorssel/README.md

@@ -1,13 +1,13 @@
 ## To build:
 
-```<!---sh-->
+``` <!---sh-->
     make all
 ```
 
 
 ## To use:
 
-```<!---sh-->
+``` <!---sh-->
     ./dorssel
     # input some text
 
@@ -17,7 +17,7 @@
 
 ## Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./try.sh
 ```
 
@@ -48,7 +48,7 @@ altering the behavior ?
 Try doing what the last part of the last command in [try.sh](try.sh) suggests.
 As in, do the following:
 
-```<!---sh-->
+``` <!---sh-->
     echo ". -..- . .-. -.-. .. ... .
     -.-. .... .- -. --. .  - .... .  .--. .-. --- --. .-. .- --  ... ---  .. -  -.. --- . ...  -. --- -  ... .... --- ..- -" | ./dorssel
 ```
@@ -91,7 +91,7 @@ invoke undefined behavior.
 
 Try:
 
-```<!---sh-->
+``` <!---sh-->
     ./dorssel < dorssel.c | ./dorssel
 ```
 
@@ -101,20 +101,20 @@ better job than most C beautifiers).
 - Filter your text twice (as in the previous sample) to obtain a version of your
 text that can be reversibly Morsified, i.e.
 
-```<!---sh-->
+``` <!---sh-->
     ./dorssel < dorssel.c | ./dorssel | ./dorssel | ./dorssel
 ```
 
 is the same as
 
-```<!---sh-->
+``` <!---sh-->
     ./dorssel < dorssel.c | ./dorssel
 ```
 
 - The file [dorssel.md](dorssel.md) contains all the information needed to
 understand this program.  For an obfuscated spoiler, try
 
-```<!---sh-->
+``` <!---sh-->
     ./dorssel < dorssel.md
 ```
 

1998/dorssel/dorssel.md

@@ -42,7 +42,7 @@ That means bits 6 and 5 set to 00 is length 1, set to 01 is length 2, etc.
 But this would mean that we would have to extract the length into a
 counter before shifting out each symbol, such as
 
-```<!---c-->
+``` <!---c-->
     length = (encoding & 96) >> 5;
     do {
 	    putchar(encoding & 1 ? '-' : '.');
@@ -62,7 +62,7 @@ We can also use the remaining bits to *include* the counter
 
 with 1 bit still to be chosen freely (let's assume it is 0).  Now we can do
 
-```<!---c-->
+``` <!---c-->
     do {
 	    putchar(encoding & 1 ? '-' : '.');
 	    encoding >>= 1;
@@ -87,7 +87,7 @@ Notice these encodings in the initialization string.  Only the coding for
 `5` needs an escape (`5 = ..... > 01111111 = '\177'`).  The way the length
 is encoded still allows the encoding to be its own counter:
 
-```<!---c-->
+``` <!---c-->
     do {
 	    putchar(encoding & 1 ? '-' : '.');
 	    encoding = (encoding + 32) >> 1;
@@ -101,7 +101,7 @@ precision, so that the actual value of the `char` remains `<= 127`.
 The character `'-'` (ASCII 45) and `'.'` (ASCII 46) are conveniently in
 sequence, so the putchar can simply be
 
-```<!---c-->
+``` <!---c-->
     putchar(45 + encoding % 2);
 ```
 
@@ -110,7 +110,7 @@ The assignment can be incorporated into the `while` control test, and a
 `do-while` loop with a body of a single expression statement can be written
 as a `while` loop with a comma operator in the test:
 
-```<!---c-->
+``` <!---c-->
     while(putchar(45 + encoding % 2), encoding = encoding + 32 >> 1);
 ```