Release 0.4.0 * Rewrite zthreads module. * zthreads.context() function returns global context object * remove `runstring` and `runfile` functions from zthreads * add actort object to zthreads * add xrun/xfork/xactor functions to zthreads which uses global context (see examples/perf2) * threads by default run in detached joinable mode * add socket:reset_monitor() method * zmq.init_ctx use raw zmq context instead of internal pointer * zloop object does not destroy its internal context * add GSSAPI/TOS/IPC_FILTER/HANDSHAKE_IVL options * add IDENTITY_FD option * zloop.new allows only one context argument. * add supports `zmq_has` function * Fix. Use int64 as socket fd on Win X64 in ffi binding.