* object.c (rb_class_inherited_p): allow iclasses to be tested for
  inheritance. [Bug #8686] [ruby-core:56174]

* test/ruby/test_method.rb: add test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42380 b2dd03c8-39d4-4d8f-98ff-823fe69b080e