NewGRF: Allow mapping a feature ID to the town scope

src/newgrf.cpp

@@ -5352,6 +5352,7 @@ static const char *_feature_names[] = {
 	"TRAMTYPES",
 	"ROADSTOPS",
 	"NEWLANDSCAPE",
+	"TOWN",
 };
 static_assert(lengthof(_feature_names) == GSF_END);
 
@@ -5490,6 +5491,7 @@ static void FeatureChangeInfo(ByteReader *buf)
 		/* GSF_TRAMTYPES */     TramTypeChangeInfo,
 		/* GSF_ROADSTOPS */     RoadStopChangeInfo,
 		/* GSF_NEWLANDSCAPE */  NewLandscapeChangeInfo,
+		/* GSF_FAKE_TOWNS */    nullptr,
 	};
 	static_assert(GSF_END == lengthof(handler));
 	static_assert(lengthof(handler) == lengthof(_cur.grffile->action0_property_remaps), "Action 0 feature list length mismatch");

src/newgrf.h

@@ -90,12 +90,12 @@ enum GrfSpecFeature : uint8 {
 	GSF_ROADSTOPS,
 
 	GSF_NEWLANDSCAPE,
+	GSF_FAKE_TOWNS,           ///< Fake (but mappable) town GrfSpecFeature for NewGRF debugging (parent scope), and generic callbacks
 	GSF_END,
 
 	GSF_REAL_FEATURE_END = GSF_NEWLANDSCAPE,
 
-	GSF_FAKE_TOWNS = GSF_END, ///< Fake town GrfSpecFeature for NewGRF debugging (parent scope)
-	GSF_FAKE_STATION_STRUCT,  ///< Fake station struct GrfSpecFeature for NewGRF debugging
+	GSF_FAKE_STATION_STRUCT = GSF_END,  ///< Fake station struct GrfSpecFeature for NewGRF debugging
 	GSF_FAKE_END,             ///< End of the fake features
 
 	GSF_ERROR_ON_USE = 0xFE,  ///< An invalid value which generates an immediate error on mapping

src/newgrf_extension.cpp

@@ -62,6 +62,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("new_landscape", 2),
 	GRFFeatureInfo("more_objects_per_grf", 1, GFTOF_MORE_OBJECTS_PER_GRF),
 	GRFFeatureInfo("more_action2_ids", 1, GFTOF_MORE_ACTION2_IDS),
+	GRFFeatureInfo("town_feature", 1),
 	GRFFeatureInfo(),
 };
 
@@ -69,6 +70,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 extern const GRFFeatureMapDefinition _grf_remappable_features[] = {
 	GRFFeatureMapDefinition(GSF_ROADSTOPS, "road_stops"),
 	GRFFeatureMapDefinition(GSF_NEWLANDSCAPE, "new_landscape"),
+	GRFFeatureMapDefinition(GSF_FAKE_TOWNS, "town"),
 	GRFFeatureMapDefinition(),
 };