PROTON-700
By not saying 'static' on previous checkin, I broke debug builds.


git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1628274 13f79535-47bb-0310-9956-ffa450edef68
add a backwords compatible pn_transport_error

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1628289 13f79535-47bb-0310-9956-ffa450edef68