Road stops: Add bit for whether stop is being drawn in the build window

docs/newgrf-roadstops-nml.html

@@ -145,6 +145,7 @@
 		<tr><td>random_bits_tile</td><td>0..255</td><td>Random bits (per tile), see also <a href="https://newgrf-specs.tt-wiki.net/wiki/NML:Stations#Base_station_variables">random_bits_station</a></td></tr>
 		<tr><td>one_way_info</td><td>RST_OWI_XXX</td><td>One-way road information of drive-through stop tile<br />XXX = TWO_WAY | WEST_BOUND | EAST_BOUND | NO_ENTRY</td></tr>
 		<tr><td>one_way_info_inferred</td><td>RST_OWI_XXX</td><td>Inferred one-way road information of drive-through stop tile<br />XXX = TWO_WAY | WEST_BOUND | EAST_BOUND | NO_ENTRY</td></tr>
+		<tr><td>drawn_in_gui</td><td>0 | 1</td><td>1 if this road stop is being drawn in the build window</td></tr>
 	</table>
 	<br />
 	Variables that require one or more parameters:

docs/newgrf-roadstops.html

@@ -318,6 +318,10 @@
 		3 - No entry<br />
 		This requires <font face="monospace">road_stops</font>, version 8.
 	</td></tr>
+	<tr><td>4</td><td>
+		1 if the road stop is being drawn in the build window<br />
+		This requires <font face="monospace">road_stops</font>, version 9.
+	</td></tr>
 	</table>
 	<br />
 	The remaining bits are reserved for future use and should be masked.

src/newgrf_extension.cpp

@@ -58,7 +58,7 @@ extern const GRFFeatureInfo _grf_feature_list[] = {
 	GRFFeatureInfo("action0_object_edge_foundation_mode", 2),
 	GRFFeatureInfo("action0_object_flood_resistant", 1),
 	GRFFeatureInfo("action0_object_viewport_map_tile_type", 1),
-	GRFFeatureInfo("road_stops", 8),
+	GRFFeatureInfo("road_stops", 9),
 	GRFFeatureInfo("new_landscape", 2),
 	GRFFeatureInfo("more_objects_per_grf", 1, GFTOF_MORE_OBJECTS_PER_GRF),
 	GRFFeatureInfo("more_action2_ids", 1, GFTOF_MORE_ACTION2_IDS),

src/newgrf_roadstop.cpp

@@ -164,6 +164,8 @@ uint32 RoadStopScopeResolver::GetVariable(uint16 variable, uint32 parameter, Get
 					RoadCachedOneWayState rcows = GetRoadCachedOneWayState(this->tile);
 					if (rcows <= RCOWS_NO_ACCESS) result |= (rcows << 2);
 				}
+			} else {
+				SetBit(result, 4);
 			}
 			return result;
 		}