proposal: add 'unsafeCoerce'

[Donald Bruce Stewart]

ndmitchell:
> Hi
> 
> I strongly support this - I have programs which have to use CPP just
> to find this single function.

Agreed. I have cpp for the very same thing. The # must go!
  
> As to the module name, its Unsafe, but it doesn't operate on data
> really, and its a function but so is everything else. Maybe we need to
> put it in Type.Unsafe, and start a new Type.* hierarchy for type level
> computation?

Hmm. Not sure. Nothing better suggests itself other than System.IO.Unsafe.

-- Don