Hi!

The printf(3) page says:
```
SYNOPSIS
       #include <stdio.h>

       int printf(const char *restrict format, ...);
[...]

       #include <stdarg.h>

       int vprintf(const char *restrict format, va_list ap);
[...]
       int vsnprintf(char *restrict str, size_t size,
                   const char *restrict format, va_list ap);
```

It might just be me, but the gap between the two blocks of functions made me think that only <stdarg.h> was needed for those latter functions, even though it's needed for va_list.

Would it be appropriate to add a second #include <stdio.h> above #include <stdarg.h> to resolve the ambiguity?

Thanks!