MW-366 Improved support for IPv6 networks - made mysqld and SST scripts to recognize []-escaped IPv6 addresses - pulled in latest Percona and MariaDB updates to SST scripts - instruct netcat and socat in wsrep_sst_xtrabackup-v2 to listen on IPv6 socket via sockopt parameter in the [sst] section of my.cnf

In summary, wsrep_node_address and wsrep_sst_receive_address can now
be set to IPv6 addresses escaped by []. Rsync SST works out ouf the
box thanks to rsync daemon listening on both IPv4 and IPv6 sockets by
default. For xtrabackup SST onver IPv6 one needs to set sockopt in
the [sst] section of joiner's configuration file to ",pf=ip6" if
using socat as a streamer or to "-6" if using netcat.