Deal with 'Delay' in case building properly

We mustn't inspect the laziness type, because we'll never have it. (This
is a bit of a hack and relies on never having two different types of
laziness in the same argument, but since that doesn't make sense anyway,
I believe this is safe!)

Fixes #1295
Merge branch 'master' of github.com:idris-lang/Idris-dev