Add move version of rcp_dynamic_cast()

include/rcp.h

@@ -174,6 +174,9 @@ public:
     {
         return T::create(std::forward<Args>(args)...);
     }
+
+    template <typename V, typename W>
+    friend rcp<V> rcp_dynamic_cast(rcp<W> && other);
 };
 
 template <typename T, typename U>
@@ -182,6 +185,20 @@ rcp<T> rcp_dynamic_cast(const rcp<U> & other)
     return rcp<T>(dynamic_cast<T *>(other.get_raw()));
 }
 
+template <typename T, typename U>
+rcp<T> rcp_dynamic_cast(rcp<U> && other)
+{
+    T * p = dynamic_cast<T *>(other.ptr);
+    if (p)
+    {
+        other.ptr = nullptr;
+        rcp<T> result;
+        result.ptr = p;
+        return result;
+    }
+    return rcp<T>();
+}
+
 #define rcp_managed_root(classname) \
     public: \
         void rcp_inc() const \