Support for newtypes

[robdockins]

Following the merge of GaloisInc/cryptol#1015, we need to add support for newtypes to cryptol-saw-core.

As a first pass, we will simply erase newtypes. They don't satisfy any typeclass constraints, so that part of the translation should be easy.

[robdockins]

I think this has been done for some time now.

[atomb]

We have an internal example where record selection to project from a newtype fails to translate.

[robdockins]

Are you able to minimize the example?

[atomb]

Just finished doing that. Here you go.

Say you have the following in newtype_bug.cry:

newtype T n = { vec : [n] }

fromT : {n} T n -> [n]
fromT x = x.vec

Then running import "newtype_bug.cry" at the SAWScript REPL leads to a panic about an invalid record selector.

[robdockins]

Ah, I see. The record selector code is type-driven and doesn't know what to do for newtypes. That shouldn't be too hard to fix.