Feature #15217: Add Resolv.current_resolver

• Status: Open
• Assignee: -
• Target version: -

[christophe971 (Christophe Maximin)]

This allows us to have a per-thread default resolver.
This change is backwards compatible and will not change the behavior of Resolv.
This commit is also adding a bunch of missing specs for Resolv.

https://github.com/ruby/ruby/pull/1978