Convert to use rta_getattr_ functions

User new functions (inspired by libmnl) to do type safe access
of routeing attributes
diff --git a/ip/ipxfrm.c b/ip/ipxfrm.c
index f55bff9..c7b3420 100644
--- a/ip/ipxfrm.c
+++ b/ip/ipxfrm.c
@@ -806,7 +806,7 @@
 			return;
 		}
 
-		lastused = *(__u64 *)RTA_DATA(tb[XFRMA_LASTUSED]);
+		lastused = rta_getattr_u64(tb[XFRMA_LASTUSED]);
 
 		fprintf(fp, "%s", strxf_time(lastused));
 		fprintf(fp, "%s", _SL_);