Correct net.createServer() API docs

Author: koichik

doc/api/net.markdown

@@ -4,11 +4,16 @@ The `net` module provides you with an asynchronous network wrapper. It contains
 methods for creating both servers and clients (called streams). You can include
 this module with `require("net");`
 
-### net.createServer(connectionListener)
+### net.createServer([options], [connectionListener])
 
 Creates a new TCP server. The `connectionListener` argument is
 automatically set as a listener for the `'connection'` event.
 
+`options` is an object with the following defaults:
+
+    { allowHalfOpen: false
+    }
+
 ### net.createConnection(arguments...)
 
 Construct a new socket object and opens a socket to the given location. When