if connect() returns EINPROGRESS one has to check connect status via getsockopt
Add tracing of socket readability and writability status
Do not distribute all messenger credit, just ensure each link has at least one credit
Make send and recv more parametrized
fix and enhance messenger and driver

error.h:
  - add new error code for pn_driver_wakeup path

messenger.h:
  - add new function pn_messenger_wakeup that tickles the driver

util.h:
  - Add object instance identification infrastructure and tracing

util.c:
  - basic implementation of objid and tracing -- really noisy

sasl.c:
  - add object identification and some tracing

engine-internal.h:
  - add object identification

dispatcher.h:
  - add object identification

dispatcher.c:
  - add tracing

engine.c:
  - add tracing

driver.c:
  - add tracing
  - return distinct error code from pn_driver_wait
    in case of pn_driver_wakeup

messenger.c:
  - add tracing
  - pn_messenger_flow: should not try to distribute
        all messenger's credit as there will be new
        connections coming in.
  - pn_messenger_tsync: wrap up in case of pn_driver_wakeup
  - pn_messenger_send: in case of idle messenger do not return
        error, but do pn_driver_wait
Merge branch 'ttlj_proton' of github.com:ttlj/qpid-proton into ttlj_proton