cannot see a constant defined in the grandparent module from doubly-nested singleton class

[tsahara]

module A
  CONST = 123
  class << self
    p 1, CONST
    class << self
      p 2, CONST
    end
  end
end

% ruby -v a.rb
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-darwin16]
1
123
2
123

% bin/mruby a.rb
1
123
trace:
	[0] a.rb:6
	[1] a.rb:5
	[2] a.rb:3
	[3] a.rb:1
a.rb:6: uninitialized constant #<Class:#<Class:A>>::CONST (NameError)

[keizo042]

I send PR that I fix the issue. plz check there are something wrong any more.