page_zip_dir_decode(): Correct the handling of the free list.

page_zip_set_extra_bytes(): Remove off-by-one error in the first loop.

page_zip_apply_log(): Replace parameter end with size, and let end=data+size.

page_zip_decompress(): Properly handle pages where the first user record has
more than REC_N_NEW_EXTRA_BYTES extra bytes.

page_delete_rec_list_end(): Remove page_zip_temp.  This operation will be
done completely in-place on page_zip.  If page_zip is specified, clear the
data bytes and the info and status bits of deleted records and clear the
removed directory slots.

page_dir_delete_slot(): Clear the last directory slot, which will be removed.