Odd behavior of ncurses with -threaded

[Edward Z. Yang]

Excerpts from Donn Cave's message of Thu Nov 11 17:07:20 -0500 2010:
> > ghc:     6.12.1
> > linux:   2.6.32
> > ncurses: 5.7
> 
> Someone probably should.  It's tempting to conclude that the bug
> is in ncurses, and perhaps it is, and maybe there's nothing to be
> done about it anyway, but a language runtime that's spewing SIGALRMs
> is going to crash into this kind of thing a lot.  I could comment a
> couple of other cases to the ticket that I've seen here or on Haskell-cafe.

I was under the impression we fixed this:

    http://hackage.haskell.org/trac/ghc/ticket/850

That is, we should be using SIGVTALRM, not SIGALRM, these days, except
under certain conditions when your operating system doesn't support
the proper timer (which Linux most assuredly does).

Edward