Portability part 1 - C99 printf

printf, sprintf, fprintf etc are now all C99 compliant. All except sprintf, which is now signaled as deprecated. This raises a few warnings about sprintf usage in the build. Some I fix with pull requests that will follow. Some others should be fixed by the respective authors.
Pre-existing: the introduction to a list (using "the following" to refer forward) should end in a colon, not a full-stop:
`Please try to do the following when writing output messages:`