Adding support to publish on custom host port ranges

Signed-off-by: Don Kjer <don.kjer@gmail.com>

Changing vendor/src/github.com/docker/libnetwork to match lindenlab/libnetwork custom-host-port-ranges-1.7 branch

docs/reference/run.md

@@ -984,6 +984,7 @@ or override the Dockerfile's exposed defaults:
                    format: ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort | containerPort
                    Both hostPort and containerPort can be specified as a range of ports.
                    When specifying ranges for both, the number of container ports in the range must match the number of host ports in the range. (e.g., `-p 1234-1236:1234-1236/tcp`)
+                   When specifying a range for hostPort only, the containerPort must not be a range.  In this case the container port is published somewhere within the specified hostPort range. (e.g., `-p 1234-1236:1234/tcp`)
                    (use 'docker port' to see the actual mapping)
     --link=""  : Add link to another container (<name or id>:alias or <name or id>)
 

docs/userguide/dockerlinks.md

@@ -50,6 +50,14 @@ container:
 And you saw why this isn't such a great idea because it constrains you to
 only one container on that specific port.
 
+Instead, you may specify a range of host ports to bind a container port to
+that is different than the default *ephemeral port range*:
+
+    $ docker run -d -p 8000-9000:5000 training/webapp python app.py
+
+This would bind port 5000 in the container to a randomly available port
+between 8000 and 9000 on the host.
+
 There are also a few other ways you can configure the `-p` flag. By
 default the `-p` flag will bind the specified port to all interfaces on
 the host machine. But you can also specify a binding to a specific