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/command_type.h

@@ -582,6 +582,11 @@ enum FlaggedCommands {
 	CMD_ID_MASK               = 0x00FF, ///< mask for the command ID
 };
 
+inline constexpr Commands operator|(const Commands &lhs, const FlaggedCommands &rhs)
+{
+	return static_cast<Commands>(static_cast<uint32_t>(lhs) | static_cast<uint32_t>(rhs));
+}
+
 static_assert(CMD_END <= CMD_ID_MASK + 1);
 
 /**