uninitialized constant Net::IMAP::Config::AttrTypeCoercion::Ractor with release 0.5.11

[cdemoulins]

The last release 0.5.11 raise an error with jruby. I think it's the same issue than for #452 and related to this commit 71c0288.

[nevans]

It's the same area of code, yeah. Sorry about that. #454 still hasn't been merged to catch this sort of thing. ☹️

[nevans]

@cdemoulins I've merged code to fix this: #530. And I added TruffleRuby to CI: #528. Unfortunately, JRuby passes for me locally but fails in CI: #529, so I haven't merged that yet. But the TruffleRuby tests should prevent this particular issue from happening to JRuby users, too.

I'll push a new release by Monday.