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/signal_type.h

@@ -53,6 +53,7 @@ struct SignalReference {
 	TileIndex tile;
 	Track track;
 };
+DECLARE_ENUM_AS_ADDABLE(SignalType)
 
 /**
  * These are states in which a signal can be. Currently these are only two, so