A few more questions about threads:

        1) is there any way to wait on the termination of single or multiple threads?
           There doesn't seem to be and this seems to be a strange oversight.

        2) What happens to Thread.t variables onces the thread they reference
           has disappeared?

        3) related to the above, what happens to
           file descriptor backing of {in,out}_channel variables once they
           are no longer referenced (i.e are those files automatically closed?)

Cheers,
Julian.