File name / module name mismatch error text

[pnwamk]

TL;DR consider swapping out Saw: => Actual: in Cryptol error messages (or similar) and playing a little with the pretty-printed alignment of the Actual and Expected columns/rows.

This isn't a huge deal but might be a small improvement.

Backstory:

I got this error message running some scripts that invoke cryptol:

[error] :1:1--1:1:
    File name does not match module name:
    Saw: Main
    Expected: keygen_implementation

I now understand what this error is saying, but initially I was a little thrown and was looking for how SAW related to the particular setup I had. Perhaps this is a one-off and I just need a cup of coffee, but if others find this potentially confusing, and given how often these two tools more and more are used either in conjunction or at least at different times by the same people, it might be nice to slightly tweak the wording (and perhaps even the indentation/alignment?), e.g.:

[error] :1:1--1:1:
    File name does not match module name:
        Actual: Main
      Expected: keygen_implementation

It may also be worth noting that the keygen_implementation file has no specified module name, which is why it defaults to Main, but the error message doesn't allude to that at all.

[RyanGlScott]

Fixed in #1419.