MEDIUM: server: change server ip address from stats socket

New command available on the stats socket to change a server addr using
the command "set server <backend>/<server> addr <ip4|ip6>"
diff --git a/doc/configuration.txt b/doc/configuration.txt
index 897e285..9fbffba 100644
--- a/doc/configuration.txt
+++ b/doc/configuration.txt
@@ -14930,6 +14930,9 @@
   is passed in number of sessions per second sent to the SSL stack. It applies
   before the handshake in order to protect the stack against handshake abuses.
 
+set server <backend>/<server> addr <ip4 or ip6 address>
+  Replace the current IP address of a server by the one provided.
+
 set server <backend>/<server> agent [ up | down ]
   Force a server's agent to a new state. This can be useful to immediately
   switch a server's state regardless of some slow agent checks for example.