Add Method#=== that invokes #call

[nomadium]

Hi folks,

This is another feature targeting Ruby 2.5 [1]: Add Method#=== that invokes #call (feature #14142).

The associated MRI test to the feature work as expected:

  def test_eqq
    assert_operator(0.method(:<), :===, 5)
    assert_not_operator(0.method(:<), :===, -5)
  end

miguel@alice:~/jruby$ PATH=$PWD/bin:$PATH jruby test/mri/runner.rb -v --color=never --tty=no --excludes=test/mri/excludes -q -n test_eqq -- ruby/test_method.rb
Run options: -v --color=never --tty=no --excludes=test/mri/excludes -q -n test_eqq --

# Running tests:

[1/1] TestMethod#test_eqq = 0.02 s
Finished tests in 0.260273s, 3.8421 tests/s, 15.3685 assertions/s.
1 tests, 4 assertions, 0 failures, 0 errors, 0 skips

ruby -v: jruby 9.3.0.0-SNAPSHOT (2.5.0) 2018-03-04 96b264b Java HotSpot(TM) 64-Bit Server VM 25.102-b14 on 1.8.0_102-b14 +jit [darwin-x86_64]

Thanks for your review and feedback.

1. Ruby 2.5 Support #4876