common/DecayCounter: forward-declare ceph::Formatter

Signed-off-by: Max Kellermann <[email protected]>

Author: MaxKellermann

src/common/DecayCounter.h

@@ -16,14 +16,15 @@
 #define CEPH_DECAYCOUNTER_H
 
 #include "include/buffer.h"
-#include "common/Formatter.h"
 #include "common/StackStringStream.h"
 #include "common/ceph_time.h"
 
 #include <cmath>
 #include <list>
 #include <sstream>
 
+namespace ceph { class Formatter; }
+
 /**
  *
  * TODO: normalize value based on some function of half_life,