sleeping

[Simon Marlow]

> Nope, that's exactly the part of Control.Concurrent which is 
> guarded with
> #ifdef __GLASGOW_HASKELL__, so it won't work with Hugs and nhc98.
> 
> Nevertheless, I'm sure every platform has a good way of 
> sleeping, so my
> proposal is to move (u)sleep out of the unix package into the base
> libraries, but I'm not sure where exactly in the hierarchy it 
> should be placed.

Somewhere under System probably, but it doesn't really fit into any of
the existing modules, and adding a whole new module seems like overkill.
Perhaps just adding it to System.IO is ok.

Remember to make the GHC implementation use threadDelay, because
System.Posix.(u?)sleep isn't thread-safe.

Cheers,
	Simon