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.

1988/applin/README.md

@@ -21,7 +21,7 @@ program.  See the [Alternate code](#alternate-code) section below for details.
 ./applin
 ```
 
-### Alternate code:
+## Alternate code:
 
 As noted above a smaller version can be used in case your `cpp` has a hard time
 with this entry.