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- if equinox says there is a new update, but the version number IS NOT
larger, we interpret that as no update (you may have gotten a newer
version by building it yourself).

- Also export ErrNoUpdateAvailable so clients don't also need to
import the equinox library to check the error.

cc @cryptix comments?

- distinguish log.Error and log.Errorf functions
- Initialize structs with field names
- A bit of unreachable code (defers)