[#MDEV-21856] XID_t::formatID has to be contrained to 4 byte size

There are two causes requiring that.
1. Engine understanding of the member has been of 4 bytes, at least in Innodb case:

 CREATE TABLE `ti` (

  `a` int(11) DEFAULT NULL

) ENGINE=InnoDB;

xa start '1','2',4611686018427387905;

  insert into ti set a=1;

xa end '1','2',4611686018427387905;

xa prepare '1','2',4611686018427387905;

xa recover;

+---------------------+--------------+--------------+------+

| formatID            | gtrid_length | bqual_length | data |

+---------------------+--------------+--------------+------+

| 4611686018427387905 |            1 |            1 | 12   |

+---------------------+--------------+--------------+------+

--error crash

xa commit '1','2',4611686018427387905;

# restart mysqld

xa recover;

ERROR 2006 (HY000): MySQL server has gone away

No connection. Trying to reconnect...

Connection id:    4

Current database: test

+----------+--------------+--------------+------+

| formatID | gtrid_length | bqual_length | data |

+----------+--------------+--------------+------+

|        1 |            1 |            1 | 12   |

+----------+--------------+--------------+------+

2. and the 2nd reason is XA replication across different platforms which
mean different sizes for ulong specified entity. Constraining it to 4 satisfies them all.

[MDEV-21856] XID_t::formatID has to be contrained to 4 byte size Created: 2020-03-02 Updated: 2020-03-09 Resolved: 2020-03-09
Status:	Closed
Project:	MariaDB Server
Component/s:	Replication, Server
Affects Version/s:	10.1, 10.2, 10.3, 10.4, 10.5
Fix Version/s:	10.5.2

[MDEV-21856] XID_t::formatID has to be contrained to 4 byte size Created: 2020-03-02 Updated: 2020-03-09 Resolved: 2020-03-09