Log Message:
net/ruby-nio4r: update to 2.5.2

Update ruby-nio4r to 2.5.2.

2.5.2 (2019-09-24)

* #220 Update to libev-4.27 & fix assorted warnings. (@ioquatix)

* #225 Avoid need for linux headers. (@ioquatix)

2.4.0 (2019-07-07)

* #211 Enable KQUEUE on macOS 10.14+. (@ioquatix)

* Bump minimum supported Ruby to 2.3. (@ioquatix)

* Assorted fixes for TruffleRuby & JRuby. (@eregon, @olleolleolle)

* Update libev to v4.25. (@ioquatix)

* Bind to ephemeral (port 0) for more reliable specs. (@ioquatix)

* Improve handling of SSL sockets and related specs. (@MSP-Greg)