Deprecated. The functionality of this module has been merged back into
the Unix module. Threaded programs can now call the functions
from module Unix directly, and still get the correct behavior
(block the calling thread, if required, but do not block all threads
in the process).
Thread-compatible system calls.
Behave as ThreadUnix.read and ThreadUnix.write, except that
Unix_error(ETIMEDOUT,_,_) is raised if no data is
available for reading or ready for writing after d seconds.
The delay d is given in the fifth argument, in seconds.