io: implement path manipulation and directory iteration on darwin

io-test/tree.c

@@ -24,7 +24,7 @@ int main(int argc, const char **argv)
 	b_directory_iterator it = {0};
 	b_directory_iterator_begin(dir, &it, B_DIRECTORY_ITERATE_PARENT_FIRST);
 	while (b_directory_iterator_is_valid(&it)) {
-		printf("%s\n", it.filename);
+		printf("%s\n", it.filepath);
 		b_directory_iterator_next(&it);
 	}