ThreadId should be Eq/Ord (and preferably Read/Show)

[George Russell]

The Concurrent library spec says ThreadId should be an instance of
Eq and Ord but ghc doesn't seem to know.  (The definition of ThreadId
seems to be in PrelConc.lhs and is:
   data ThreadId = ThreadId ThreadId#
I think you need a "derives (Eq,Ord)" in there.

As a matter of fact I would also like ThreadId to be Read/Show,
even though that isn't in the documentation.