Unify set of derives for all the enums (i.e. adding `Hash` elsewhere, at least for C-like enums).

[sagudev]

This change on its own seems fine, although we probably should try to unify this set of derives for all the enums (i.e. adding Hash elsewhere, at least for C-like enums).

Originally posted by @DJMcNab in #148 (review)