Allow local port control on net_socket connections

doc/classes/PacketPeerUDP.xml

@@ -28,6 +28,13 @@
 				[b]Note:[/b] Connecting to the remote peer does not help to protect from malicious attacks like IP spoofing, etc. Think about using an encryption technique like SSL or DTLS if you feel like your application is transferring sensitive information.
 			</description>
 		</method>
+		<method name="get_local_port" qualifiers="const">
+			<return type="int">
+			</return>
+			<description>
+				Returns the local port to which this peer is bound.
+			</description>
+		</method>
 		<method name="get_packet_ip" qualifiers="const">
 			<return type="String">
 			</return>

doc/classes/StreamPeerTCP.xml

@@ -9,6 +9,18 @@
 	<tutorials>
 	</tutorials>
 	<methods>
+		<method name="bind">
+			<return type="int" enum="Error">
+			</return>
+			<argument index="0" name="port" type="int">
+			</argument>
+			<argument index="1" name="host" type="String" default="&quot;*&quot;">
+			</argument>
+			<description>
+				Opens the TCP socket, and binds it to the specified local address.
+				This method is generally not needed, and only used to force the subsequent call to [method connect_to_host] to use the specified [code]host[/code] and [code]port[/code] as source address. This can be desired in some NAT punchthrough techniques, or when forcing the source network interface.
+			</description>
+		</method>
 		<method name="connect_to_host">
 			<return type="int" enum="Error">
 			</return>
@@ -17,7 +29,7 @@
 			<argument index="1" name="port" type="int">
 			</argument>
 			<description>
-				Connects to the specified [code]host:port[/code] pair. A hostname will be resolved if valid. Returns [constant OK] on success or [constant FAILED] on failure.
+				Connects to the specified [code]host:port[/code] pair. A hostname will be resolved if valid. Returns [constant OK] on success.
 			</description>
 		</method>
 		<method name="disconnect_from_host">
@@ -41,6 +53,13 @@
 				Returns the port of this peer.
 			</description>
 		</method>
+		<method name="get_local_port" qualifiers="const">
+			<return type="int">
+			</return>
+			<description>
+				Returns the local port to which this peer is bound.
+			</description>
+		</method>
 		<method name="get_status">
 			<return type="int" enum="StreamPeerTCP.Status">
 			</return>

doc/classes/TCP_Server.xml

@@ -9,6 +9,13 @@
 	<tutorials>
 	</tutorials>
 	<methods>
+		<method name="get_local_port" qualifiers="const">
+			<return type="int">
+			</return>
+			<description>
+				Returns the local port this server is listening to.
+			</description>
+		</method>
 		<method name="is_connection_available" qualifiers="const">
 			<return type="bool">
 			</return>

doc/classes/UDPServer.xml

@@ -123,6 +123,13 @@
 	<tutorials>
 	</tutorials>
 	<methods>
+		<method name="get_local_port" qualifiers="const">
+			<return type="int">
+			</return>
+			<description>
+				Returns the local port this server is listening to.
+			</description>
+		</method>
 		<method name="is_connection_available" qualifiers="const">
 			<return type="bool">
 			</return>