PROTON-677: added support for detach

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1627098 13f79535-47bb-0310-9956-ffa450edef68
PROTON-679: patch from dominic for manual credit mode

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1627102 13f79535-47bb-0310-9956-ffa450edef68
PROTON-680: link and delivery accessors (patch from dominic)

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1627106 13f79535-47bb-0310-9956-ffa450edef68
 PROTON-693: Make pn_url_t a proper pn_class object, hashable & comparable.

git-svn-id: https://svn.apache.org/repos/asf/qpid/proton/trunk@1627155 13f79535-47bb-0310-9956-ffa450edef68
PROTON-696: Rearrange the header files:
- Reduce transitive header inclusions
- Remove proton/util.h and move its contents to src/util.h. All
  the defined symbols were internal.
- Stop including with lines like #include "../blah.h" as this
  isn't needed anymore.
(Fixes windows breakage from PROTON-676)