Add road stops flag for drive-through stops only

docs/newgrf-roadstops-nml.html

@@ -80,6 +80,8 @@
 			<span class="indent">Do not show one way road overlay sprites, this should only be set if different graphics are provided for the different one-way states using the <span class="code">one_way_info</span> variable.</span></p>
 			<p><b>RST_GENERAL_FLAG_NO_CATENARY</b><br />
 			<span class="indent">Do not show catenary graphics. (This only takes effect from <span class="code">road_stops</span> version 2).</span></p>
+			<p><b>RSF_GENERAL_FLAG_DRIVE_THROUGH_ONLY</b><br />
+			<span class="indent">Only allow drive-through stops (not bay stops). (This only takes effect from <span class="code">road_stops</span> version 2).</span></p>
 		</td></tr>
 		<tr><td>minimum_bridge_height</td><td>Array of 6 items [0..255, ...]</td><td>Minimum clearances required for a bridge for each of the <a href="#roadstop_views">6 views/rotations</a> (or 0 to not allow any bridge). Values are given in height level units (1 level == 8px).</td></tr>
 		<tr><td>disallowed_bridge_pillars</td><td>Array of 6 items [bitmask(RST_BRIDGE_PILLAR_FLAG_, ...), ...]</td><td>

docs/newgrf-roadstops.html

@@ -151,6 +151,7 @@
 	<tr><td>0</td><td>1</td><td>Callback 141 needs random bits in variable 10</td></tr>
 	<tr><td>1</td><td>2</td><td>Do not show one way road overlay sprites, this should only be set if different graphics are provided for the different one-way states using bits 0..1 of variable 50.</td></tr>
 	<tr><td>2</td><td>4</td><td>Do not catenary graphics.</br>This requires <font face="monospace">road_stops</font>, version 2.</td></tr>
+	<tr><td>3</td><td>8</td><td>Only allow drive-through stops (not bay stops).</br>This requires <font face="monospace">road_stops</font>, version 2.</td></tr>
 	</table>
 	The default value is 0 (no flags enabled).
 	</p>