Switch prettyprinter layout engine from `layoutSmart` to `layoutPretty`.
Switch prettyprinter layout engine from `layoutSmart` to `layoutPretty`.

This avoids an exponential slowdown that occurs with `layoutSmart`
in combination with nested lists or lists of tuples.

Fixes #1274.

GaloisInc/cryptol,GaloisInc/cryptol,GaloisInc/cryptol