branch for PROTON-225

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1445892 13f79535-47bb-0310-9956-ffa450edef68
PROTON-225: modify transport API to support internal I/O buffer

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1445894 13f79535-47bb-0310-9956-ffa450edef68
PROTON-225: review feedback

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446333 13f79535-47bb-0310-9956-ffa450edef68
PROTON-225: more doc changes

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446334 13f79535-47bb-0310-9956-ffa450edef68
PROTON-225: update to latest trunk

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446621 13f79535-47bb-0310-9956-ffa450edef68
PROTON-235: fix SASL buffering problem

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446688 13f79535-47bb-0310-9956-ffa450edef68
PROTON-222: give messenger visibility into the amount of buffered output

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446691 13f79535-47bb-0310-9956-ffa450edef68
PROTON-222: modify new interface to return bool rather than size_t

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446692 13f79535-47bb-0310-9956-ffa450edef68
PROTON-222: add simple test reproducer

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/branches/kgiusti-proton-225@1446693 13f79535-47bb-0310-9956-ffa450edef68
PROTON-222, PROTON-225, PROTON-235: merge from task branch kgiusti-proton-225

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1446697 13f79535-47bb-0310-9956-ffa450edef68