Replace java_kind_of? with kind_of? to support JRuby-9.3.0.0

[ThomasKoppensteiner]

Fixes Issue: #155

[ThomasKoppensteiner]

@michaelklishin can you please have a look?

[ThomasKoppensteiner]

@olleolleolle I have seen your comment on the JRuby issue (jruby/jruby#6862 (comment)).

FYI: The test for the long header conversion (https://github.com/ruby-amqp/march_hare/blob/master/spec/higher_level_api/integration/basic_consume_spec.rb#L158) worked for me locally with this branch (JRuby-9.3.0.0 and .kind_of?).

[olleolleolle]

@ThomasKoppensteiner That sounds good. I'm in favour of the change.

In order for it to be visible for everyone, I'd love to have CI runs.

[headius]

Sorry for the inconvenience removing this method! It has been around since very old Java integration days, but since we started mimicking the Java class hierarchy with Ruby types (like 15 years ago) it has not been needed. I guess you really never can delete anything!

Let us know if there are any further issues here.

[ThomasKoppensteiner]

Rebase master after #158 is merged.

[olleolleolle]

LGTM!

[michaelklishin]

Thank you! That was easier than I expected it to ;)

[ThomasKoppensteiner]

Thank you for merging the PRs.
When will you release the fix?

[michaelklishin]

I don't know why but I cannot gem push to rubygems.org, it runs into a network connectivity issue of some kind.

[michaelklishin]

Apparently this is why: https://github.com/jruby/jruby/issues/6871

[michaelklishin]

OK, built the gem on JRuby 9.3 and pushed using CRuby 3.0.