[mio] 回收计数器

vnt/src/util/counter/adder.rs

@@ -49,6 +49,13 @@ impl SingleU64AdderInner {
         unsafe { *self.ptr }
     }
 }
+impl Drop for SingleU64AdderInner{
+    fn drop(&mut self) {
+        unsafe {
+            let _ = Box::from_raw(self.ptr);
+        }
+    }
+}
 
 unsafe impl Send for SingleU64AdderInner {}