Merge branch 'master' into jgrpp

# Conflicts:
#	src/airport_gui.cpp
#	src/build_vehicle_gui.cpp
#	src/direction_type.h
#	src/gfx_type.h
#	src/group_gui.cpp
#	src/misc_gui.cpp
#	src/rail_gui.cpp
#	src/road_gui.cpp
#	src/signs_gui.cpp
#	src/slope_func.h
#	src/smallmap_gui.cpp
#	src/terraform_gui.cpp
#	src/toolbar_gui.cpp
#	src/town_gui.cpp
#	src/town_type.h
#	src/vehicle_type.h
#	src/widget_type.h

src/intro_gui.cpp

@@ -378,7 +378,7 @@ struct SelectGameWindow : public Window {
 	}
 };
 
-static const NWidgetPart _nested_select_game_widgets[] = {
+static constexpr NWidgetPart _nested_select_game_widgets[] = {
 	NWidget(WWT_CAPTION, COLOUR_BROWN), SetDataTip(STR_INTRO_CAPTION, STR_NULL),
 	NWidget(WWT_PANEL, COLOUR_BROWN),
 		NWidget(NWID_VERTICAL), SetPIP(0, WidgetDimensions::unscaled.vsep_wide, 0), SetPadding(WidgetDimensions::unscaled.sparse),