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: garbled "don't a message" needs a verb, probably `*Log*`, `don't *Log* a message using several`, but it's still ugly phrasing.
`Normally, keep each message atomic and on one line: don't split related information across several *Log* calls; don't put newlines in *Log* messages.`
Suitably flowed, of course.