Add spec for doubles compiled under ARC

* Lenny's issue: [#54033775]
* Specs fail, this is a placeholder for a future fix
Fixes deallocation of CedarDoubles after messaged on secondary thread with a block argument.
Use atomic association policy
This addition still causes EXC_BAD_ACCESS
Defer retention of invocation args to last moment

- It appears that copying/retaining blocks before performing an
  invocation interferes with ARC smarts along method boundaries