* src/Sbitset.c (Sbitset__new_on_obstack): Use Sbitset instead
of char*.
(Sbitset__isEmpty): Use Sbitset instead of char*.
* src/Sbitset.h (Sbitset): Make it a pointer to unsigned char
instead of char. This helps to avoid casting errors.
(Sbitset__or): Use Sbitset instead of char*.
Reported by Jim Meyering.
* src/Sbitset.h (SBITSET__INDEX__CONVERSION_SPEC): New, "zu"
because Sbitset__Index is size_t.
* src/Sbitset.c (Sbitset__fprint): Use it instead of %d.