more fixes/tweaks about cancelled lindas

* bumped version to 3.8.5
* linda:limit() returns lanes.cancel_error on a limited linda
* lanes.genlock() and lanes.genatomic() support cancelled lindas by
returning lanes.cancel_error whenever appropriate
* fixed a possible Lua stack overflow when calling linda:dump()
* fixed cases where linda:send() and linda:receive() would not return
lanes.cancel_error when they should