* The OP_RESIZE seat operation has been renamed to OP_RESIZE_FLOATING,
and OP_RESIZE_TILING has been introduced.
* Similar to the above, seat_begin_resize and handle_resize_motion have
been renamed and tiling variants introduced.
* resize.c's resize_tiled has to be used, so container_resize_tiled has
been introduced in resize.c to allow external code to call it.