Further support for partial application lambda re-sugaring by supporting coerced vars

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The current re-sugaring is ad-hoc and we can improve it for example, given

    let f (x:obj) (y:obj) = x |> string

Before this fix the following expression decompilation

    <@ 2 |> f "2" @> |> decompile

would be

    "2 |> let x = "2" in fun y -> f x y"

due to coercion throwing off our pattern matching. But after this fix we'll have

    "2 |> f "2""

Original issue reported on code.google.com by stephen....@gmail.com on 5 Jul 2011 at 3:22