Drop offical support for MySQL 5.5

[walro]

MySQL 5.5 is EoL.

I choose to still support v1 row events as you may still run MySQL 5.6 and 5.7 using them (default was changed to v2 in MySQL 5.6). V1 is deprecated in MySQL 8.0 though. Resources:

• https://dev.mysql.com/doc/refman/5.6/en/replication-options-binary-log.html#sysvar_log_bin_use_v1_row_events
• https://dev.mysql.com/doc/refman/5.7/en/replication-options-binary-log.html#sysvar_log_bin_use_v1_row_events
• https://dev.mysql.com/doc/refman/8.0/en/replication-options-binary-log.html#sysvar_log_bin_use_v1_row_events

Close #45