MDEV-18173 Assertion `o->ind == vers_end' or `o->ind == vers_start' failed in dict_table_t::instant_column

ha_innobase_inplace_ctx::create_key_defs(): Replaces
innobase_create_key_defs().

dict_index_t::contains_col_or_prefix(): Replaces
dict_index_contains_col_or_prefix().

Closes #988

Bug was introduced in this commit:

  commit: a9ca8198
      Call alloc() instead of realloc()
      Use alloc() if we don't need original string (avoid copy)
      Removed not needed test of str_length in sql_string.cc

copy_if_not_alloced() was forgotten when changing realloc()'s to alloc()'s.
Changing it now.

This was introduced in 1a7a0189
MDEV-16557 Remove INNOBASE_SHARE::idx_trans_tbl

ha_innobase::innobase_get_index: remove incorrect assertion.
Index nullability is checked in subsequent ifs.

Closes #1079

The fil_system_t::name_hash was removed already earlier,
in commit 05863142.
The fil_space_t::name_hash was thus made an orphan data field.

log_group_file_header_flush(): Use a stack-local variable
instead of the heap-allocated buffers.

Closes #1060

MDEV-18173 Assertion `o->ind == vers_end' or `o->ind == vers_start' failed in dict_table_t::instant_column

Closes #965

Closes #983, #984

MDEV-18224 MTR's internal check of the test case 'innodb.recovery_shutdown' failed due to extra #sql-ib*.ibd files

The test innodb.recovery_shutdown would occasionally fail,
because recovered incomplete transactions would be conflicting
with DROP TABLE, causing the background drop table queue to be invoked.

Add a slow shutdown before dropping the tables, so that the
recovered transactions will be rolled back. Starting with MDEV-14705,
normal shutdown would abort the rollback of recovered transactions.

Change mysql_alter_user to log alter user command.

The purpose of buf_pool->flush_rbt is to ensure that
buf_pool->flush_list is ordered by oldest_modification.
This should speed up multi-pass redo log application
(when the buffer pool is not large enough to accommodate
all pages that were modified since the latest log checkpoint).

The buf_pool->flush_rbt is not being used after redo log has
been applied. It could be better to always flush pages in
the ascending order of oldest_modification. Currently, whenever
a page is first modified, it will be moved to the start of the
buf_pool->flush_list, overtaking blocks whose oldest_modification
could be much older.

buf_flush_insert_sorted_into_flush_list(): Merge into
buf_flush_insert_into_flush_list().

buf_flush_recv_note_modification(): Remove.
The function buf_flush_note_modification() can be invoked instead.

Fix one more bug in "DDL redo" phase in prepare
If table was renamed, and then new table was created with the old name,
prepare can be confused, and .ibd can end up with wrong name.

Fix the order of how DDL fixup is applied , once again - ".new" files
should be processed after renames.

btr_cur_pessimistic_insert(): Do not attempt to convert the
metadata BLOB to external storage if it has already been converted.
It could have been converted by btr_cur_pessimistic_update().
Relax some over-zealous assertions.

dtuple_convert_big_rec(): Assert that the metadata BLOB has
not been converted yet.

If, during backup
1) Innodb table is dropped (after being copied to backup) and then
2) Before backup finished, another Innodb table is renamed, and new name
is the name of the dropped table in 1)

then, --prepare fails with assertion, as DDL fixup code in prepare
did not handle this specific case.

The fix is to process drops before renames, in prepare DDL-"redo" phase.

btr_cur_instant_init_low(): Fix the typo in the computation
of the trx_id_offset of a metadata record.

Simplified mutex code. MutexDebug uses OSMutex instead of
atomic operations now.

MDEV-15022 - travis: add versioning to test suite

MDEV-15578 - travis: add zstd for osx