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	Kill Type.splitRepFunTys
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splitRepFunTys was a Bad Function that split up a function type
looking through even recursive newtypes.  Alas, it diverged if
when we had a recursive newtype with a function whose result was
the newtype itself.

I've replaced it with ordinary splitFunTys, plus a new function
Type.dropForAlls, which does what you would expect.