Change heading level of 'Original code'

In the case where we recommend trying the alternate code first, the
lower section is 'Original code' but this was at heading level 3 when
discussion suggests 2 so this was done as well:

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

2006/sloane/README.md

@@ -41,7 +41,7 @@ make CDEFINE="-DS=0" clobber alt
 ./sloane.alt
 ```
 
-### Original code:
+## Original code:
 
 Should you wish to see the original without having to mess with the compiler
 line, try: