Replace lazy_static with once_cell

[Yesterday17]

No description provided.

[hwittenborn]

Could you merge this repo's master branch into your's so that the CI can run @Yesterday17?

[LingMan]

Could you merge this repo's master branch into your's so that the CI can run @Yesterday17?

That would create useless merge commits polluting the history. The correct operation would be to rebase onto current master. Just FYI.

[hwittenborn]

I was planning on doing a squash merge once the PR got in anyway @LingMan, so it shouldn't matter much.

[LingMan]

Ah, I see. The squash button does still add the title of the merge commit to the commit message, but it is an improvement over leaving them separate.
Personally I'm always annoyed when maintainers squash my carefully separated commits into one messy pile. Since there's only one real commit here that obviously doesn't apply though. (Not to mention that I'm not the author here, so I'll shut up now.)

[Yesterday17]

Could you merge this repo's master branch into your's so that the CI can run @Yesterday17?

Done.

[hwittenborn]

I'm assuming the other crates used in the library have extern crate definitions in the root because of an old Rust version that's being targeted, but I'll have to double check once the crate gets an MSRV figured out (see #85).

This would technically be a breaking change, and I'd probably end up putting this inside a v3 of colored, which is already planned if #139 ends up happening. I'll probably end up making a v2 branch or something, and then I can get this merged in.

[kurtlawrence]

Could this been done with https://doc.rust-lang.org/std/sync/struct.Once.html ?