Patch release 1.6.2

• Fixed issues
  • [#371]:(#371 include in concurrency/utility.hpp
  • The _hold for detach was being done on the executor instead of the continuation. The result was a (silenced) broken exception getting thrown if detach() is called on a ready exception.
    This would trigger an exception which is caught internally in a packaged task and dropped.

   stlab::make_ready_future(stlab::immediate_executor).detach();

  • Fixed an issue with the serial queue using a "temporary" executor which was copied into the future shared state.
  • Added stealing to blocking_get
  • Also cleaned up blocking_get implementation.
  • blocking_get_for() added
  • Fix for make_exceptional_future and improvements blocking_get_for added
  • deprecated blocking_get() with timeout
  • Fixing bugs and naming our threads
  • Fixed issue with backoff
  • min() duration on a clock apparently is not a minimum length duration as documented, but is a negative duration... instead we us a single tick.
  • Update utility.hpp