(bitsetv_alloc, bitsetv_create, bitsetv_free,

bitsetv_zero, bitsetv_ones, bitsetv_transitive_closure,
bitsetv_reflexive_transitive_closure):
Use bitset_bindex, not int or unsigned int or size_t, to count bits.

(bitsetv_alloc): Use size_t, not unsigned int, to count bytes.

(bitsetv_dump, debug_bitsetv):
Use bitset_windex instead of unsigned int.
Use proper printf formats for widths of integer types.

(bitsetv_alloc): Check for arithmetic overflow when computing sizes.