A straightforward and hopefully uncontroversial refactor to improve consistency.
- 
Move the decision whether to translate an individual error message to where it is defined. This simplifies call sites: no more InitError(Untranslated(SomeFunction(...))).
- 
Make all functions in util/error.hconsistently return abilingual_str. We’ve decided to use this as error message type so let’s roll with it.
This has no functional changes: no messages are changed, no new translation messages are defined.
Also make a function static that can be static.