Merge branch 'custom_bridgeheads' into jgrpp

# Conflicts:
#	docs/landscape.html
#	src/bridge_map.h
#	src/pbs.cpp
#	src/saveload/company_sl.cpp
#	src/saveload/extended_ver_sl.cpp
#	src/settings_type.h
#	src/signal.cpp
#	src/train_cmd.cpp
#	src/tunnel_map.h
#	src/tunnelbridge_cmd.cpp
#	src/tunnelbridge_map.h
#	src/vehicle.cpp
#	src/viewport.cpp

src/rail.h

@@ -441,4 +441,16 @@ extern uint8 _sorted_railtypes_size;
  */
 #define FOR_ALL_SORTED_RAILTYPES(var) for (uint8 index = 0; index < _sorted_railtypes_size && (var = _sorted_railtypes[index], true) ; index++)
 
+/** Enum holding the signal offset in the sprite sheet according to the side it is representing. */
+enum SignalOffsets {
+	SIGNAL_TO_SOUTHWEST,
+	SIGNAL_TO_NORTHEAST,
+	SIGNAL_TO_SOUTHEAST,
+	SIGNAL_TO_NORTHWEST,
+	SIGNAL_TO_EAST,
+	SIGNAL_TO_WEST,
+	SIGNAL_TO_SOUTH,
+	SIGNAL_TO_NORTH,
+};
+
 #endif /* RAIL_H */