Update Mapgen VoxelManipulator on buffer invalidation

src/map.h

@@ -493,6 +493,8 @@ public:
 	// Database version
 	void loadBlock(std::string *blob, v3s16 p3d, MapSector *sector, bool save_after_load=false);
 
+	void updateVManip(v3s16 pos);
+
 	// For debug printing
 	virtual void PrintInfo(std::ostream &out);
 
@@ -550,6 +552,8 @@ public:
 	void blitBackAll(std::map<v3s16, MapBlock*> * modified_blocks,
 			bool overwrite_generated = true);
 
+	bool m_is_dirty;
+
 protected:
 	bool m_create_area;
 	Map *m_map;