Merge branch 'polyline_track_tool' into jgrpp

# Conflicts:
#	src/rail_cmd.cpp
#	src/rail_gui.cpp
#	src/viewport.cpp
#	src/viewport_func.h

src/window.cpp

@@ -2846,7 +2846,7 @@ static void MouseLoop(MouseClick click, int mousewheel)
 				/* FALL THROUGH */
 			case MC_LEFT:
 				DEBUG(misc, 2, "Cursor: 0x%X (%d)", _cursor.sprite, _cursor.sprite);
-				if (!HandleViewportClicked(vp, x, y) &&
+				if (!HandleViewportClicked(vp, x, y, click == MC_DOUBLE_LEFT) &&
 						!(w->flags & WF_DISABLE_VP_SCROLL) &&
 						_settings_client.gui.left_mouse_btn_scrolling) {
 					_scrolling_viewport = w;