record will fit or need external storage.
btr_page_get_sure_split_rec(): Estimate the free space of an empty
compressed page.
page_zip_rec_needs_ext(): New function, to replace existing tests whether
external storage is needed.
Replace btr_page_get_level() with page_is_leaf() where possible.
row_purge_upd_exist_or_extern(): Remove obsolete TODO comment.
dtuple_convert_big_rec(): Replace a flag variable with goto.
flag of records. The flags may only be updated in heap-allocated
copies of records.
btr_root_raise_and_insert(),
btr_page_split_and_insert(),
btr_cur_insert_if_possible(),
btr_cur_optimistic_insert(),
btr_cur_pessimistic_insert(),
page_cur_tuple_insert(),
page_cur_insert_rec_low(): Add parameters "ext" and "n_ext".
dtuple_convert_big_rec(): Make parameter "ext" const.
