Ticket #455: allocate pjsua call id in round robin fashion

git-svn-id: https://svn.pjsip.org/repos/pjproject/trunk@1717 74dad513-b988-da41-8d7b-12977e46ad98
diff --git a/pjsip/include/pjsua-lib/pjsua_internal.h b/pjsip/include/pjsua-lib/pjsua_internal.h
index 205faee..943eb69 100644
--- a/pjsip/include/pjsua-lib/pjsua_internal.h
+++ b/pjsip/include/pjsua-lib/pjsua_internal.h
@@ -215,6 +215,7 @@
     pjsua_config	 ua_cfg;		/**< UA config.		*/
     unsigned		 call_cnt;		/**< Call counter.	*/
     pjsua_call		 calls[PJSUA_MAX_CALLS];/**< Calls array.	*/
+    pjsua_call_id	 next_call_id;		/**< Next call id to use*/
 
     /* Buddy; */
     unsigned		 buddy_cnt;		    /**< Buddy count.	*/