Merge branch 'master' into jgrpp

# Conflicts:
#	src/industry_cmd.cpp
#	src/landscape.cpp
#	src/object_cmd.cpp
#	src/rail_cmd.cpp
#	src/script/api/script_tile.cpp
#	src/table/settings/difficulty_settings.ini
#	src/table/settings/world_settings.ini
#	src/terraform_cmd.cpp
#	src/tilearea_type.h
#	src/tree_cmd.cpp
#	src/tree_cmd.h
#	src/tree_gui.cpp
#	src/water_cmd.cpp

src/tilearea_type.h

@@ -154,7 +154,9 @@ public:
 	/**
 	 * Allocate a new iterator that is a copy of this one.
 	 */
-	virtual TileIterator *Clone() const = 0;
+	virtual std::unique_ptr<TileIterator> Clone() const = 0;
+
+	static std::unique_ptr<TileIterator> Create(TileIndex corner1, TileIndex corner2, bool diagonal);
 };
 
 /** Iterator to iterate over a tile area (rectangle) of the map. */
@@ -201,9 +203,9 @@ public:
 		return *this;
 	}
 
-	virtual TileIterator *Clone() const
+	virtual std::unique_ptr<TileIterator> Clone() const
 	{
-		return new OrthogonalTileIterator(*this);
+		return std::make_unique<OrthogonalTileIterator>(*this);
 	}
 };
 
@@ -227,11 +229,6 @@ public:
 		PREFETCH_NTA(&_m[ta.tile]);
 	}
 
-	/** Some compilers really like this. */
-	virtual ~OrthogonalPrefetchTileIterator()
-	{
-	}
-
 	/**
 	 * Get the tile we are currently at.
 	 * @return The tile we are at, or INVALID_TILE when we're done.
@@ -259,11 +256,6 @@ public:
 		}
 		return *this;
 	}
-
-	virtual OrthogonalPrefetchTileIterator *Clone() const
-	{
-		return new OrthogonalPrefetchTileIterator(*this);
-	}
 };
 
 /** Iterator to iterate over a diagonal area of the map. */
@@ -299,9 +291,9 @@ public:
 
 	TileIterator& operator ++();
 
-	virtual TileIterator *Clone() const
+	virtual std::unique_ptr<TileIterator> Clone() const
 	{
-		return new DiagonalTileIterator(*this);
+		return std::make_unique<DiagonalTileIterator>(*this);
 	}
 };