Log Message:
Update databases/percona-toolkit to 2.2.19.

- Recheck the list of slaves while OSC runs
- pt-osc should error if server is a slave in row based
  replication
- pt-table-checksum should force replica table charset to utf8
- Added --create-table-engine param to pt-heartbeat
- SlowLogParser is able to handle dates in RFC339 format for MySQL
  5.7
- pt-kill leaks memory each time it kills a query
- Large BLOB/TEXT/BINARY Produces NULL Checksum
- Fixed pt-archiver deletes wrong rows #103
- Added --slave-user and --slave-password to
  pt-online-schema-change & pt-table-sync
- Handle GTID ranges where the left-side integer is larger than 9
- Remove extra word 'default' from the --verbose help
- add enum column type to is_char check so that values are
  properly quoted