Changing heading level of 'Alternate code'

Change level 3 (###) to level 2 (##):

    sgit -e 's/^### \(Alternate code\)/## \1/g' '*README.md'

which is the same as:

    sgit -e 's/^### Alternate code/## Alternate code/g' '*README.md'

This is per discussion in GitHub.

1989/jar.1/README.md

@@ -26,7 +26,7 @@ NOTE: this will run the program itself:
 make clobber all
 ```
 
-### Alternate code:
+## Alternate code:
 
 This code, which prints something slightly different, is provided as well.
 

1989/ovdluhe/README.md

@@ -35,7 +35,7 @@ by chance or is killed.
 ./ovdluhe < README.md
 ```
 
-### Alternate code:
+## Alternate code:
 
 The author suggested that one varies the definition of `P` from 2 through 10. As
 it's a `#define` it's easy to set up. To use try:

1989/paul/README.md

@@ -18,7 +18,7 @@ out. See [alternate code](#alternate-code) below for more details.
 ./paul
 ```
 
-### Alternate code:
+## Alternate code:
 
 This version was described by the author like:
 

1989/tromp/README.md

@@ -48,7 +48,7 @@ place and the winner is the
 loser](https://web.archive.org/web/20181023221954/https://www.chicagotribune.com/news/ct-xpm-2002-07-31-0207310310-story.html) :-)
 
 
-### Alternate code:
+## Alternate code:
 
 The author provided an alternate version of the code with some improvements. See
 the judges' additional remarks in the author's remarks, for more details.