Merge commit 'a8b575671894ffe1329ef37dca4989c0e60d70f5'

These merges are becoming more awful every time

Conflicts:
	src/ai/ai_gui.cpp
	src/build_vehicle_gui.cpp
	src/cheat_gui.cpp
	src/company_gui.cpp
	src/depot_gui.cpp
	src/dock_gui.cpp
	src/error_gui.cpp
	src/genworld_gui.cpp
	src/misc_gui.cpp
	src/network/network_content_gui.cpp
	src/network/network_gui.cpp
	src/newgrf_gui.cpp
	src/news_gui.cpp
	src/rail_gui.cpp
	src/rev.cpp.in
	src/road_gui.cpp
	src/settings_gui.cpp
	src/settings_gui.h
	src/signs_gui.cpp
	src/station_gui.cpp
	src/table/settings.ini
	src/terraform_gui.cpp
	src/toolbar_gui.cpp
	src/toolbar_gui.h
	src/vehicle_gui.cpp
	src/video/sdl_v.cpp
	src/viewport.cpp
	src/widget.cpp
	src/widgets/settings_widget.h

src/smallmap_gui.h

@@ -63,6 +63,7 @@ protected:
 
 	static SmallMapType map_type; ///< Currently displayed legends.
 	static bool show_towns;       ///< Display town names in the smallmap.
+	static int max_heightlevel;   ///< Currently used/cached maximum heightlevel.
 
 	static const uint LEGEND_BLOB_WIDTH = 8;              ///< Width of the coloured blob in front of a line text in the #WID_SM_LEGEND widget.
 	static const uint INDUSTRY_MIN_NUMBER_OF_COLUMNS = 2; ///< Minimal number of columns in the #WID_SM_LEGEND widget for the #SMT_INDUSTRY legend.
@@ -148,6 +149,7 @@ protected:
 		return Company::IsValidID(_local_company) ? 1U << _local_company : 0xffffffff;
 	}
 
+	void RebuildColourIndexIfNecessary();
 	uint GetNumberRowsLegend(uint columns) const;
 	void SelectLegendItem(int click_pos, LegendAndColour *legend, int end_legend_item, int begin_legend_item = 0);
 	void SwitchMapType(SmallMapType map_type);