Add DISABLE_CLASS_COPY macro (and use it)

Use this macro to disallow copying of an object using the assignment
operator or copy constructor.  This catches otherwise silent-but-deadly
mistakes such as "ServerMap map = env->getMap();" at compile time.

If so desired, it is still possible to copy a class, but it now requires
an explicit call to memcpy or std::copy.

src/objdef.h

@@ -90,6 +90,9 @@ protected:
 	INodeDefManager *m_ndef;
 	std::vector<ObjDef *> m_objects;
 	ObjDefType m_objtype;
+
+private:
+	DISABLE_CLASS_COPY(ObjDefManager);
 };
 
 #endif