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.
How many ``sprintf`` are left after converting to ``snprintf`` and ``xsnprintf``? Basically there should be none if we want to enable this, and that includes nova and enterprise. We can still submit the file, of course, so that the warnings can be easily enabled, but it should be disabled so existing warnings don't start bugging everyone.

Also, I think it would be helpful if the message mentions ``xsnprintf`` as well, since it is often a more appropriate replacement (in most cases of using ``sprintf``, the author does not anticipate any overflow).