Add yet another 4 bytes of capability flags for new MariaDB functionality:

• from server->client in handshake packet V1
  • client parse version info to be sure that it is MariaDB server
  • server put flags in last 4 of unused 10 (bytes 14-17)
• from client->server (only if server mariadb and version is >= 10.2) V1
  • client sets 'client_long_password=0' and 'client_protocol_41=1'
  • puts flag in last 4 of 23 unused

Move CLIENT_PROGRESS flag to the new flag space.