Basically removing it from the __scanf_input structure and specializing
it at format sites. The reason is that pretending it's the end of the
stream after the limit is reached does not work because we have to
return EOF at end of stream but not when the limit is hit. So we have to
handle it explicitly, and since we do, no need to have it in the
structure too.
Mostly an initialization problem. But I also optimized the check by
making the bound a maximal unsigned integer when there is no bound,
since __scanf_peek() is used a lot.
