added iteration API to map and hash

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487479 13f79535-47bb-0310-9956-ffa450edef68
replaced delivery buffer data structure with delivery map

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487485 13f79535-47bb-0310-9956-ffa450edef68
removed redundant back pointers

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487508 13f79535-47bb-0310-9956-ffa450edef68
added cast for older compilers

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487802 13f79535-47bb-0310-9956-ffa450edef68
NO-JIRA: use cast to avoid conversion warnings from older C++ compilers

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1487827 13f79535-47bb-0310-9956-ffa450edef68