This package provides functions to fork threads and wait for their result,
whether it's an exception or a normal value.
Besides waiting for the termination of a single thread this packages also
provides functions to wait for a group of threads to terminate.
This package is similar to the 'threadmanager', 'async' and 'spawn' packages.
The advantages of this package are:
* Simpler API.
* More efficient in both space and time.
* No space-leak when forking a large number of threads.
* Correct handling of asynchronous exceptions.
* GHC specific functionality like 'forkOn' and 'forkIOWithUnmask'.
