Issue with find_type and child classes in Ruby 2.0.0

[meh]

#! /usr/bin/env ruby
require 'ffi'

module Test
    extend FFI::Library

    ffi_lib FFI::Library::LIBC

    callback :bug, [], :void

    class Foo < FFI::Struct
        class Bar < FFI::Struct
            layout :a, :bug
        end

        layout :b, Bar
    end
end

/home/meh/.gem/ruby/2.0.0/gems/ffi-1.5.0/lib/ffi/types.rb:57:in `find_type': unable to resolve type 'bug' (TypeError)
        from /home/meh/.gem/ruby/2.0.0/gems/ffi-1.5.0/lib/ffi/struct.rb:316:in `find_type'
        from /home/meh/.gem/ruby/2.0.0/gems/ffi-1.5.0/lib/ffi/struct.rb:309:in `find_field_type'
        from /home/meh/.gem/ruby/2.0.0/gems/ffi-1.5.0/lib/ffi/struct.rb:351:in `array_layout'
        from /home/meh/.gem/ruby/2.0.0/gems/ffi-1.5.0/lib/ffi/struct.rb:261:in `layout'
        from lol.rb:13:in `<class:Bar>'
        from lol.rb:12:in `<class:Foo>'
        from lol.rb:11:in `<module:Test>'
        from lol.rb:4:in `<main>'

This used to work on 1.9.

[ghost]

Looks like this is due to this behavioural change in 2.0 http://tenderlovemaking.com/2012/09/07/protected-methods-and-ruby-2-0.html

Looks like it should be pretty easy to fix.