6.4.3 and threaded RTS problems

[Simon Marlow]

Could someone on MacOS X try the 6.4.x branch again?  I just committed a fix 
that makes the threaded RTS more stable on Solaris, and I'm hoping it clears up 
the problems on MacOS X too.  Remember to re-enable -threaded in 
ghc/compiler/Makefile if you previously disabled it.

If this does indeed fix things, then I think we'll probably tag this branch as 
6.4.3, but I doubt we'll actually do a full release of 6.4.3 at this stage since 
6.6 should be stable enough for most people.

Cheers,
	Simon