Avoid need for rcp_managed() call in rcp root class

include/rcp.h

@@ -96,7 +96,7 @@ public:
     }
 };
 
-#define rcp_root() \
+#define rcp_root(classname) \
     public: \
         void rcp_inc() const \
         { \
@@ -110,7 +110,8 @@ public:
             } \
         } \
     private: \
-        mutable std::atomic<int> ref_count{0}
+        mutable std::atomic<int> ref_count{0}; \
+    rcp_managed(classname)
 
 #define rcp_managed(classname) \
     public: \