doc: Update zmq_socket(3) for 2.0.8 API changes

doc/zmq_socket.txt

@@ -216,22 +216,24 @@ is connected to at least one _node_. When a pipeline stage is connected to
 multiple _nodes_ data is load-balanced among all connected _nodes_.
 
 
-ZMQ_DOWNSTREAM
-^^^^^^^^^^^^^^
-A socket of type 'ZMQ_DOWNSTREAM' is used by a pipeline _node_ to send messages
+ZMQ_PUSH
+^^^^^^^^
+A socket of type 'ZMQ_PUSH' is used by a pipeline _node_ to send messages
 to downstream pipeline _nodes_. Messages are load-balanced to all connected
 downstream _nodes_. The _zmq_recv()_ function is not implemented for this
 socket type.
 
-When a 'ZMQ_DOWNSTREAM' socket enters an exceptional state due to having
-reached the high water mark for all downstream _nodes_, or if there are no
-downstream _nodes_ at all, then any linkzmq:zmq_send[3] operations on the
-socket shall block until the exceptional state ends or at least one downstream
-_node_ becomes available for sending; messages are not discarded.
+When a 'ZMQ_PUSH' socket enters an exceptional state due to having reached the
+high water mark for all downstream _nodes_, or if there are no downstream
+_nodes_ at all, then any linkzmq:zmq_send[3] operations on the socket shall
+block until the exceptional state ends or at least one downstream _node_
+becomes available for sending; messages are not discarded.
+
+Deprecated alias: 'ZMQ_DOWNSTREAM'.
 
 [horizontal]
-.Summary of ZMQ_DOWNSTREAM characteristics
-Compatible peer sockets:: 'ZMQ_UPSTREAM'
+.Summary of ZMQ_PUSH characteristics
+Compatible peer sockets:: 'ZMQ_PULL'
 Direction:: Unidirectional
 Send/receive pattern:: Send only
 Incoming routing strategy:: N/A
@@ -239,16 +241,18 @@ Outgoing routing strategy:: Load-balanced
 ZMQ_HWM option action:: Block
 
 
-ZMQ_UPSTREAM
-^^^^^^^^^^^^
-A socket of type 'ZMQ_UPSTREAM' is used by a pipeline _node_ to receive
-messages from upstream pipeline _nodes_. Messages are fair-queued from among
-all connected upstream _nodes_. The _zmq_send()_ function is not implemented
-for this socket type.
+ZMQ_PULL
+^^^^^^^^
+A socket of type 'ZMQ_PULL' is used by a pipeline _node_ to receive messages
+from upstream pipeline _nodes_. Messages are fair-queued from among all
+connected upstream _nodes_. The _zmq_send()_ function is not implemented for
+this socket type.
+
+Deprecated alias: 'ZMQ_UPSTREAM'.
 
 [horizontal]
-.Summary of ZMQ_UPSTREAM characteristics
-Compatible peer sockets:: 'ZMQ_DOWNSTREAM'
+.Summary of ZMQ_PULL characteristics
+Compatible peer sockets:: 'ZMQ_PUSH'
 Direction:: Unidirectional
 Send/receive pattern:: Receive only
 Incoming routing strategy:: Fair-queued