Add optional RAI Field

Routing Area Information is an optional Field described in 3GPP TS 29.060 7.7.3
it can be added with command line option rai, in the dot separated format MCC.MNC.LAC.RAC
example :  --rai 208.10.65535.255

Signed-off-by: Yann BONNAMY <yann_bonnamy@yahoo.fr>
Signed-off-by: Harald Welte <laforge@gnumonks.org>
diff --git a/gtp/pdp.h b/gtp/pdp.h
index d826d77..aea5df7 100644
--- a/gtp/pdp.h
+++ b/gtp/pdp.h
@@ -192,6 +192,8 @@
   int    rattype_given;  /* Radio Access Technology Type given*/
   struct ul255_t    userloc;  /* User Location Information  */
   int    userloc_given;  /* User Location Information  given*/
+  struct ul255_t    rai;  /* Routing Area Information  */
+  int    rai_given;  /* Routing Area Information  given*/
   struct ul255_t    mstz;  /* MS Time Zone */
   int    mstz_given;  /* MS Time Zone given*/
   struct ul255_t    imeisv;  /* IMEI Software Version */