Merge branch 'master' into jgrpp

# Conflicts:
#	regression/regression/result.txt
#	src/autoreplace_cmd.cpp
#	src/industry_gui.cpp
#	src/landscape.cpp
#	src/network/network_content.cpp
#	src/newgrf_roadstop.cpp
#	src/pathfinder/yapf/yapf_ship.cpp
#	src/road_gui.cpp
#	src/saveload/ai_sl.cpp
#	src/saveload/saveload.h
#	src/saveload/vehicle_sl.cpp
#	src/station.cpp
#	src/station_gui.cpp
#	src/video/cocoa/cocoa_ogl.h
#	src/video/sdl2_opengl_v.h
#	src/video/video_driver.hpp
#	src/video/win32_v.h
#	src/widget_type.h
#	src/widgets/dropdown.cpp
#	src/widgets/dropdown_type.h
#	src/window.cpp

src/script/api/script_group.hpp

@@ -129,7 +129,9 @@ public:
 	 * Get the number of engines in a given group.
 	 * @param group_id The group to get the number of engines in.
 	 * @param engine_id The engine id to count.
-	 * @pre IsValidGroup(group_id) || group_id == GROUP_ALL || group_id == GROUP_DEFAULT.
+	 * @pre ScriptEngine::IsValidEngine(engine_id).
+	 * @pre (IsValidGroup(group_id) && ScriptEngine::GetVehicleType(engine_id) == GetVehicleType(group_id)) ||
+	     group_id == GROUP_ALL || group_id == GROUP_DEFAULT.
 	 * @game @pre ScriptCompanyMode::IsValid().
 	 * @return The number of engines with id engine_id in the group with id group_id.
 	 */