* Added `RCIF` (basedefs.h)
  * Fix assertion error in `iwstree_remove()` (iwstree.h)
  * Allows zero key/value placeholders in `iwstree_iter_next()` (iwstree.h)
  * Added `iwstree_put_overwrite` (iwstree.h)
  * Added  iwstree iteration API (iwstree.h)
  * Added `iwpool_used_size` (iwpool.h)
  * Added `iwstree_int64_cmp` (iwstree.h)
  * Added `IW_DEPRECATED` (basedefs.h)