Enable vehicle variable 61 for ships

Bump multi_part_ships feature version, add to documentation

docs/newgrf-additions.html

@@ -48,6 +48,7 @@
 	<li><a href="#a0objects">Action 0 - Objects</a></li>
 	<li><a href="#variable-mapping">Action 14 - Variable Mapping for Variational Action 2</a></li>
 	<li><a href="#varaction2_additional_types">Variational Action 2 - Additional Types</a></li>
+	<li><a href="#varaction2_vehicles">Variational Action 2 - Vehicles</a></li>
 	<li><a href="#varaction2_station">Variational Action 2 - Stations</a></li>
 	<li><a href="#varaction2_railtypes">Variational Action 2 - Railtypes</a></li>
 	<li><a href="#varaction2_object">Variational Action 2 - Objects</a></li>
@@ -779,6 +780,10 @@
 	Bit 7 of the <font face="monospace">mode</font> byte must be set to use temporary variable 0x100 instead.</p>
 	<p>Note: Using temporary variable 0x100 as the offset should be used with caution.</p>
 	<br />
+	<h3 id="varaction2_vehicles"><a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Vehicles">Variational Action 2 - Vehicles</a></h3>
+	<h4 id="varaction2_vehicles_var61">Query variable of n-th vehicle in chain (61)</h4>
+	<p>This variable is also enabled for ships if indicated by the feature name: <font face="monospace">multi_part_ships</font>, version 2.</p>
+	<br />
 	<h3 id="varaction2_station"><a href="https://newgrf-specs.tt-wiki.net/wiki/VariationalAction2/Stations">Variational Action 2 - Stations</a></h3>
 	<h4 id="varaction2_station_var42">Track type in purchase list (42)</h4>
 	<p>This is indicated by the feature name: <font face="monospace">varaction2_station_var42</font>, version 1</p>

src/newgrf_engine.cpp

@@ -772,7 +772,7 @@ static uint32 VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object,
 			}
 
 		case 0x61: // Get variable of n-th vehicle in chain [signed number relative to vehicle]
-			if (!v->IsGroundVehicle() || parameter == 0x61) {
+			if (!(v->IsGroundVehicle() || v->type == VEH_SHIP) || parameter == 0x61) {
 				/* Not available */
 				break;
 			}

src/newgrf_extension.cpp

@@ -70,7 +70,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("town_zone_callback", 1, GFTOF_TOWN_ZONE_CALLBACK),
 	GRFFeatureInfo("varaction2_towns_town_xy", 1),
 	GRFFeatureInfo("more_varaction2_types", 1, GFTOF_MORE_VARACTION2_TYPES),
-	GRFFeatureInfo("multi_part_ships", 1, GFTOF_MULTI_PART_SHIPS),
+	GRFFeatureInfo("multi_part_ships", 2, GFTOF_MULTI_PART_SHIPS),
 	GRFFeatureInfo("more_stations_per_grf", 1),
 	GRFFeatureInfo(),
 };