proton 0.10 blocker

[Gordon Sim]

The latest proton code is causing crashes in qpid-cpp tests that use it. 
I've tracked the problem down to the fix for PROTON-905[1] and proposed 
an enhancement to that fix, https://reviews.apache.org/r/36509/, which 
avoids the crash.

Could someone who understands the logic controlling the lifecycle of 
pn_session_t and pn_link_t objects in detail review and approve this please?


[1] https://git-wip-us.apache.org/repos/asf?p=qpid-proton.git;h=653f4e5