The dbg! macro expands to nothing in no_std mode, so variables that are
only used for debugging prompt unused variable warnings.
Also, allow unstable_features in no_std builds, since they use
feature(alloc), which is an unstable feature.
This makes it a little more consistent; now, "cretonne" is never capitalized
in identifier, path, or URL contexts. It is capitalized in natural
language contexts when referring to the project.
