Expose zmq_unbind.
Merge branch 'master' of git://github.com/whitequark/ocaml-zmq into whitequark-master

Conflicts:
	src/caml_zmq_stubs.c
Merge branch 'whitequark-master'
- Add zmq function names to indicate cause of error in case of errors when calling zmq clib.
Merge branch 'master' of github.com:issuu/ocaml-zmq