the insert buffer bitmap.

ibuf_set_free_bits_func(): Never disable redo logging.

ibuf_update_free_bits_zip(): Remove.

btr_page_reorganize_low(), page_zip_reorganize(): Do not update the insert
buffer bitmap.  Instead, document that callers will have to take care of it,
and adapt the callers.

btr_compress(): On error, reset the insert buffer free bits.

btr_cur_insert_if_possible(): Do not modify the insert buffer bitmap.

btr_compress(), btr_cur_optimistic_insert(): On compressed pages,
reset the insert buffer bitmap.  Document why.

btr_cur_update_alloc_zip(): Document why it is necessary and sufficient
to reset the insert buffer free bits.

btr_cur_update_in_place(), btr_cur_optimistic_update(),
btr_cur_pessimistic_update(): Update the free bits in the same
mini-transaction.  Document that the mini-transaction must be
committed before latching any further pages.  Verify that this
is the case in all execution paths.

row_ins_sec_index_entry_by_modify(), row_ins_clust_index_entry_by_modify(),
row_undo_mod_clust_low(): Because these functions call
btr_cur_update_in_place(), btr_cur_optimistic_update(), or
btr_cur_pessimistic_update(), document that the mini-transaction must be
committed before latching any further pages.  Verify that this is the case
in all execution paths.