This cop will flag extra spacing which seems arbitrary. It
will not flag extra spacing used to align tokens if the same
characters appear in the same column on contiguous lines.
* Use the `ConditionVariable` primitive to fix rece between stopped
receiver Thread and its wake signal.
* Race was only observable via synthetical benchmarks and explicit
sleeps between unlocking receiver mutex and Thread.stop
* Simplifies code a lot as thread must not be passed around anymore
