NO-JIRA: Added missing const qualifiers to Buffer get functions.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1485510 13f79535-47bb-0310-9956-ffa450edef68
QPID-4866: HA support for failover exchange

Add support for the "amq.failover" exchange with new HA, to support migration of
clients that used this facility with the old cluster.

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1485511 13f79535-47bb-0310-9956-ffa450edef68