Add a new mysqld command line parameter to choose
between MariaDB-5.3 and MySQL-5.6 low level formats
for TIME, DATETIME, TIMESTAMP:

mysqld --mysql56-temporal-format

Add a corresponding read-only global system variable @@mysql56_temporal_format.

Consider switching to the MySQL56 temporal format as the default.
The advantage of the MySQL56 format is that it uses
separate type codes MYSQL_TYPE_TIME2, MYSQL_TYPE_TIMESTAMP2,
MySQL_TYPE_DATETIME2 and put the column precisions in metadata
in the binary log, which can help to fix the problem reported in MDEV-5377.