Add an activeobject manager to hold active objects (#7939)

* Add an activeobject manager to hold active objects
* Add unittests

src/server/activeobjectmgr.h

@@ -0,0 +1,45 @@
+/*
+Minetest
+Copyright (C) 2010-2018 nerzhul, Loic BLOT <loic.blot@unix-experience.fr>
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU Lesser General Public License for more details.
+
+You should have received a copy of the GNU Lesser General Public License along
+with this program; if not, write to the Free Software Foundation, Inc.,
+51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+*/
+
+#pragma once
+
+#include <functional>
+#include <vector>
+#include "../activeobjectmgr.h"
+#include "serverobject.h"
+
+namespace server
+{
+class ActiveObjectMgr : public ::ActiveObjectMgr<ServerActiveObject>
+{
+public:
+	void clear(const std::function<bool(ServerActiveObject *, u16)> &cb);
+	void step(float dtime,
+			const std::function<void(ServerActiveObject *)> &f) override;
+	bool registerObject(ServerActiveObject *obj) override;
+	void removeObject(u16 id) override;
+
+	void getObjectsInsideRadius(
+			const v3f &pos, float radius, std::vector<u16> &result);
+
+	void getAddedActiveObjectsAroundPos(const v3f &player_pos, f32 radius,
+			f32 player_radius, std::set<u16> &current_objects,
+			std::queue<u16> &added_objects);
+};
+} // namespace server