A page with multiple records or deleted records still does not compress
or decompress properly.
buf_flush_init_for_writing(): Initialize block->page_zip properly so that all
assertions in page0zip can be enabled.
page_zip_decompress(): Note that corrupt data should not lead to assertions.
page_zip_dir_set(): Correct the interface. Fix off-by-one error.
page_zip_dir_get(): Fix off-by-one error.
page0zip.c: Replace n_heap with n_dense and add comments about
the infimum and supremum records whenever we subtract 2 from heap_no.
Fix some programming errors.
buf0flu.c: Allocate the temporary buffer from buf_frame_alloc().
page_zip_simple_validate(): Do not assert page_zip->m_start >= PAGE_DATA.
page_zip_compress(): Replace some assertions with page_zip_simple_validate(),
and do not assert anything about page_zip->data contents.
page_zip_validate(): Do not compare the page trailer bytes.
page_zip_write(): Assert that the entire page headers match and
that page_zip->m_start >= PAGE_DATA.
page_dir_set_n_slots(): Add debug assertion that there will be enough space
available in the modification log of the compressed page.
page_trailer_get_len(): Simplify the formula. Make more use of the function.
page_set_max_trx_id(), page_update_max_trx_id(): Add parameter page_zip.
Check that page_zip_decompress() is never called after modifying the
header or trailer of the compressed page, i.e., that page_zip_decompress()
will restore the uncompressed page as it was before the failed operation.
page_header_reset_last_insert(): Add page_zip parameter.
rec_get_next_ptr(): Return a pointer to the same page, or NULL.
page_dir_delete_slot(): Fix off-by-one errors.
Add page_zip parameter to page_dir_slot_set_rec().
Improve the documentation of the page_zip parameters in page0page.
Add function page_trailer_get_len().
Implement page_zip_write_header().
Add page_zip parameter to btr_page_set_ functions.
Allow page_copy_rec_list_end() to be called with invalid new_page_zip
if the page has been newly created.
