add TCP User Timout Option (RFC 5482)

Allow one to send the TCP User Timeout Option described in RFC 5482 in
a crafted TCP segment.

Author: jeffbencteux

scapy/layers/inet.py

@@ -213,7 +213,8 @@ class IPOption_SDBM(IPOption):
                 8 : ("Timestamp","!II"),
                 14 : ("AltChkSum","!BH"),
                 15 : ("AltChkSumOpt",None),
-                25 : ("Mood","!p")
+                25 : ("Mood","!p"),
+                28 : ("UTO", "!H")
                 },
               { "EOL":0,
                 "NOP":1,
@@ -224,7 +225,8 @@ class IPOption_SDBM(IPOption):
                 "Timestamp":8,
                 "AltChkSum":14,
                 "AltChkSumOpt":15,
-                "Mood":25
+                "Mood":25,
+                "UTO":28
                 } )
 
 class TCPOptionsField(StrField):