Better version logging when starting with JRuby

[donv]

Currently puma logs version info at startup with JRuby like this:

* Version 3.1.0 (jruby 2.2.3), codename: El Niño Winter Wonderland

Listing that we are using JRuby is really useful. Listing the compatibility level of JRuby vs MRI is only useful for JRuby 1.7.x which can support either MRI 1.8.7 or 1.9.3. JRuby 9000 only supports one version of MRI.

I would like the version log to be something like this:

* Version 3.1.0 (ruby 2.2.3 jruby 9.0.5.0), codename: El Niño Winter Wonderland

That would be

• "ruby"
• RUBY_VERSION
• RUBY_ENGINE
• RUBY_ENGINE_VERSION

The order is not important for us as long as there are no ambiguities, and actually only the RUBY_ENGINE and RUBY_ENGINE_VERSION are interesting for us, but I imagine the RUBY_VERSION may be useful for others. Just to be clear

RUBY_ENGINE + RUBY_ENGINE_VERSION

would be enough for us.

[donv]

Thanks!