Hot load core ZMQ functions

Do so instead of a call to `zmq-load` at top-level.

closes #17

* zmq.el: Replace top-level `zmq-load` call with aliasing of core ZMQ
functions to `zmq-load`, but only if the core functionality hasn't
been loaded yet.  Loading of the core functionality will overwrite
these aliased definitions with the proper ones.

zmq.el

@@ -652,7 +652,67 @@ Emacs process."
                       (recursive-edit))))))))
       (user-error "Modules are not supported"))))
 
-(zmq-load)
+(unless (featurep 'zmq-core)
+  (dolist (fun '(zmq--cleanup-globrefs
+                 zmq-socket
+                 zmq-send
+                 zmq-recv
+                 zmq-bind
+                 zmq-connect
+                 zmq-join
+                 zmq-unbind
+                 zmq-disconnect
+                 zmq-leave
+                 zmq-close
+                 zmq-proxy
+                 zmq-proxy-steerable
+                 zmq-socket-monitor
+                 zmq-socket-set
+                 zmq-socket-get
+                 zmq-context
+                 zmq-context-terminate
+                 zmq-context-shutdown
+                 zmq-context-get
+                 zmq-context-set
+                 zmq-message
+                 zmq-message-size
+                 zmq-message-data
+                 zmq-message-more-p
+                 zmq-message-copy
+                 zmq-message-move
+                 zmq-message-close
+                 zmq-message-set
+                 zmq-message-get
+                 zmq-message-recv
+                 zmq-message-send
+                 zmq-message-gets
+                 zmq-message-routing-id
+                 zmq-message-set-routing-id
+                 zmq-message-group
+                 zmq-message-set-group
+                 zmq-poll
+                 zmq-poller
+                 zmq-poller-add
+                 zmq-poller-modify
+                 zmq-poller-remove
+                 zmq-poller-destroy
+                 zmq-poller-wait
+                 zmq-poller-wait-all
+                 zmq-version
+                 zmq-has
+                 zmq-z85-decode
+                 zmq-z85-encode
+                 zmq-curve-keypair
+                 zmq-curve-public
+                 zmq-equal
+                 zmq-message-p
+                 zmq-socket-p
+                 zmq-context-p
+                 zmq-poller-p))
+    (defalias fun
+      (lambda (&rest args)
+        (zmq-load)
+        (apply fun args)))))
 
 (provide 'zmq)