Auto merge of #7400 - popzxc:restrict-locales, r=Manishearth

New lint: `disallowed_script_idents`

This PR implements a new lint to restrict locales that can be used in the code,
as proposed in #7376.

Current concerns / unresolved questions:

- ~~Mixed usage of `script` (as a Unicode term) and `locale` (as something that is easier to understand for the broad audience). I'm not sure whether these terms are fully interchangeable and whether in the current form it is more confusing than helpful.~~ `script` is now used everywhere.
- ~~Having to mostly copy-paste `AllowedScript`. Probably it's not a big problem, as the list of scripts is standardized and is unlikely to change, and even if we'd stick to the `unicode_script::Script`, we'll still have to implement custom deserialization, and I don't think that it will be shorter in terms of the amount of LoC.~~ `unicode::Script` is used together with a filtering deserialize function.
- Should we stick to the list of "recommended scripts" from [UAX #31](http://www.unicode.org/reports/tr31/#Table_Recommended_Scripts) in the configuration?

*Please write a short comment explaining your change (or "none" for internal only changes)*

changelog: ``[`disallowed_script_idents`]``

r? `@Manishearth`

0 files changed, 0 insertions, 0 deletions