respondsToSelector isn't properly guarding against calling this method
on unsupported platforms, possibly because it existed as a private
method in OS X before 10.9. For example, attempting to build this on
OS X 10.8 fails with the error:
no visible @interface for 'NSTimer' declares the selector 'setTolerance:'
Since the default tolerance is 0 anyway, this can be removed without
adverse effect.
procedure is meant to be run on, so introduce yet another StdScheduler
extra method StartOnCurrentThread which on Mac OS X does the actual run
loop registration stuff and needs to be called from the actual thread
the scheduler is supposed to run on
StdSchedulerMac: Remove SCHAdditions objects again
Nicolas Hake