Upgrade to JGroups 3.5.0.Beta3

Released. Major new feature compared to Beta1:

• Messages are now always looped back (mcasts are discarded when copies
  are received)
  https://issues.jboss.org/browse/JGRP-1765

• DONT_LOOPBACK flag: mesages can now be dropped at the transport level
  https://issues.jboss.org/browse/JGRP-1816

• Removed bottleneck when sending a message to a non-existent dest
  https://issues.jboss.org/browse/JGRP-1815

• UNICAST3: connections to non-members are now closed more quickly
  https://issues.jboss.org/browse/JGRP-1814

• SHARED_LOOPBACK_PING: new discovery protocol which always discovers
  members in the same JVM. Used by unit tests.
  https://issues.jboss.org/browse/JGRP-1809

• Hardened code for generating seqnos in UNICAST3 and NAKACK2
  https://issues.jboss.org/browse/JGRP-1807