Mixed

- better auto name
- doc update
- tests, crash in perform.

NEWS.txt:
- disable optimization warning that cause too much questions and is probably not useful.(Frederic B.)
Also to explain more. I think is completely useless (and potentially harmful) We are already using a standard type that can be passed directly to printf with the appropriate format string.

If you really want to keep this change, I would ask that you justify it.