iproute: Make it possible to specify index on link creation

The RTM_NEWLINK message accepts ifi_index non-zero value and lets
creation of links with given index (if it's free, or course). This
functionality is available since linux-v3.5.

This patch makes this API available via ip tool.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
diff --git a/include/utils.h b/include/utils.h
index a3e310e..a4b5b4c 100644
--- a/include/utils.h
+++ b/include/utils.h
@@ -156,5 +156,5 @@
 struct iplink_req;
 int iplink_parse(int argc, char **argv, struct iplink_req *req,
 		char **name, char **type, char **link, char **dev,
-		int *group);
+		int *group, int *index);
 #endif /* __UTILS_H__ */