Integrate new cost assignment version.

[abizjak]

Purpose

Integrate reduce costs for P7.

This is a very minor change compared to #1135 . The main annoyance is that tests needed to be updated because of the both cost changes in P7 and parametrization of module lookup by protocol version.

Checklist

• My code follows the style of this project.
• The code compiles without warnings.
• I have performed a self-review of the changes.
• I have documented my code, in particular the intent of the
  hard-to-understand areas.
• (If necessary) I have updated the CHANGELOG.