Merge pull request #457 from hintjens/master

Reworking zsock_t integration
Merge pull request #460 from hintjens/master

Problem: zloop broken
When an item is removed from a zlist_t, maybe some clean work should be done.

If zlist_free_fn is set, callback this function. If autofree is set, call free to the item.
Merge pull request #462 from amyangfei/patch

a memory leak bug fix
Merge pull request #461 from hintjens/master

Fixed  breaking changes to API (sock_t * vs. void *)
Merge pull request #463 from hintjens/master

Reader methods should take zsock_t
Assertion failure in zsockopt.c:965

zsocket_set_linger: Assertion `rc == 0 ... ' failed.

Caused by using zctx_t type for global_context, so that it was trying
to shut down sockets the old way on process exit.

Solution: move global context creation/shutdown to zsys, and use plain
zmq context reference.

Note: this plus new zactor class will result in deprecated classes:
zctx, zmutex, zthread, zsocket, zsockopt.
Initial empty zactor class
Trivial comment fix
Added builds/msvc and packaging/ to source packages

Fixes #464
Allow CZMQ code to use zmq_ctx_new/term

Needs macro to backport these to libzmq/2.x
Adding zmq_ctx_init/term support for libzmq/3.x
Don't install test binaries into bindir