BINLOG_SPLIT_ALTER added
now master and slave has same sequence

The XDES_CLEAN_BIT is always set for every element of
the page allocation bitmap in the extent descriptor pages.
Do not bother touching it, to avoid redundant writes.

xdes_set_free<bool free>(): Replaces xdes_set_bit().

The page allocation bitmaps in the extent descriptor pages
contain two bits per page: XDES_FREE_BIT and XDES_CLEAN_BIT,
which is unused. Simplify read access.

xdes_is_free(descr,mtr): Remove. Use !xdes_get_n_used(descr) instead.

xdes_is_free(): Replaces xdes_get_bit(), xdes_mtr_get_bit().

xdes_find_free(): Replaces xdes_find_bit().

fsp_seg_inode_page_get_nth_inode(): Remove the redundant parameters
physical_size, mtr.

fsp_seg_inode_page_find_used(), fsp_seg_inode_page_find_free():
Remove the redundant parameter mtr.

Since commit 5d596064
fil_page_type_is_index() expects uint16_t, not ulint.

fsp_alloc_seg_inode_page(): Ever since
commit 3926673c
all newly allocated pages are zero-initialized.
Assert that this is the case for the FSEG_ID fields.
(Side note: before that fix, other parts of the pages
could contain nonzero garbage.)

btr_store_big_rec_extern_fields(): Remove the redundant initialization
of the most significant 32 bits of BTR_EXTERN_LEN. InnoDB never supported
BLOBs that are longer than 4GiB. In fact, dtuple_convert_big_rec()
would write emit an error message if a clustered index record tuple would
exceed 1,000,000,000 bytes in length.

PageConverter::update_index_page(): Invoke lower-level writes directly.

The function mach_read_ulint() is a wrapper for the lower-level
functions mach_read_from_1(), mach_read_from_2(), mach_read_from_8().
Invoke those functions directly, for better readability of the code.

mtr_t::read_ulint(), mtr_read_ulint(): Remove. Yes, we will lose the
ability to assert that the read is covered by the mini-transaction.
We would still check that on writes, and any writes that
wrongly bypass mini-transaction logging would likely be caught by
stress testing with Mariabackup.

Always use the MLOG_MEMSET record for writing FIL_NULL,
because it is more compact.

MDEV-17553 Enable setting start datetime for interval partitioned history of system versioned tables

* Explicit STARTS syntax
* SHOW CREATE
* Default STARTS rounding depending on INTERVAL type
* Warn when STARTS timestamp is later than query time
* Fix uninitialized Lex->create_last_non_select_table under
  mysql_unpack_partition()

Default STARTS rounding depending on INTERVAL type

If STARTS clause is omitted, default one is assigned with value
derived from query timestamp. The rounding is done on STARTS value
depending on INTERVAL type:

SECOND: no rounding is done;
MINUTE: timestamp seconds is set to 0;
HOUR: timestamp seconds and minutes are set to 0;
DAY, WEEK, MONTH and YEAR: timestamp seconds, minutes and hours are
set to 0 (the date of rotation is kept as current date).

A conflict between MDEV-19514 (b42294bc)
and MDEV-20934 (d7a24017)
was resolved. We will not invoke the function ibuf_delete_recs()
from ibuf_merge_or_delete_for_page(). Instead, we will add that
logic to the function ibuf_read_merge_pages().

Due to MDEV-12288, the slow shutdown in MariaDB 10.3 will include
resetting the DB_TRX_ID for all inserted records. This might
cause the 60-second shutdown_server timeout to be exceeded.
Let us wait for the purge to complete before initiating slow shutdown.

dict_index_add_to_cache(): Make the 'index' a reference to a pointer,
so that the caller will avoid the expensive call to
dict_index_get_if_in_cache_low().

Due to a data corruption bug that may have occurred a long time earlier
(possibly involving physical backup and MySQL Bug #69122, which was
addressed in commit f166ec71)
it seems possible that the InnoDB change buffer might end up containing
entries, while no buffered changes exist according to the change buffer
bitmap pages in the .ibd files.

ibuf_delete_recs(): New function, to be invoked on slow shutdown only.
Remove all buffered changes for a specific page.

ibuf_merge_or_delete_for_page(): If the change buffer bitmap is clean
and a slow shutdown is in progress, invoke ibuf_delete_recs().
We do not want to do that during normal operation, due to the additional
overhead that is involved. The bitmap page should be consistent with
the change buffer in the first place.