gdbinit: make starpu-memusage show the used memory size

tools/gdbinit

@@ -766,7 +766,7 @@ define starpu-memusage
   set scheduler-locking on
   set $node = 0
   while $node < _starpu_descr.nnodes
-    printf "\n\nNode %u (%dMiB):\n", $node, global_size[$node] >> 20
+    printf "\n\nNode %u (%d/MiB/%dMiB):\n", $node, used_size[$node] >> 20, global_size[$node] >> 20
     set $total = 0
     set $total_b = 0
     set $wt = 0