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.

1984/mullender/README.md

@@ -25,7 +25,7 @@ correctly.  In later years, machine dependent code was discouraged. An alternate
 version that will work with other systems is provided as alternate code below.
 
 
-### Alternate code:
+## Alternate code:
 
 An alternate version exists which allows one to enjoy this entry on systems
 other than a [VAX-11](https://en.wikipedia.org/wiki/VAX-11) or