+/* Moves an element in ARRAY, which consists of COUNT elements of
+ SIZE bytes each, from OLD_IDX to NEW_IDX, shifting around
+ other elements as needed. Runs in O(abs(OLD_IDX - NEW_IDX))
+ time. */
+void move_element (void *array, size_t count, size_t size,
+ size_t old_idx, size_t new_idx);
+