Fix broken module namespacing in ActiveResource when using Ruby 1.9

Following namespacing use case is broken when using Ruby 1.9:

class Author < ActiveRecord::Base
end

module Api
  class Book < ActiveResouce::Base
  end
end

Let's say XML contains <book><author><name>John</name></author>....

Api::Book.first.author.class.to_s #=>
  Ruby 1.8.7: "Api::Book::Author" (namespaced, correct),
  Ruby 1.9: "Author" (toplevel, broken)

This is caused by differences in the implementation of mod.const_get? and mod.const_defined? between Ruby 1.8 and 1.9.

• http://railsapi.com/doc/ruby-v1.8/classes/Module.html#M000994
• http://railsapi.com/doc/ruby-v1.9.2/classes/Module.html#M001257

Also, see http://eigenclass.org/hiki/Changes+in+Ruby+1.9#l33 for more background information.

This patch fixes this by passing the 2nd inherit argument as false for mod.const_get? and mod.const_defined? when trying to lookup an existing resource, in the case of Ruby 1.9.