introduce RCLASS_CLONED flag for inline cache.

Methods on duplicated class/module refer same constant inline
cache (IC). Constant access lookup should be done for cloned
class/modules but inline cache doesn't check it.
To check it, this patch introduce new RCLASS_CLONED flag which
are set when if class/module is cloned (both orig and dst).
[Bug #15877]

test/ruby/test_module.rb

@@ -2418,6 +2418,39 @@ class TestModule < Test::Unit::TestCase
     }
   end
 
+  module CloneTestM_simple
+    C = 1
+    def self.m; C; end
+  end
+
+  module CloneTestM0
+    def foo; TEST; end
+  end
+
+  CloneTestM1 = CloneTestM0.clone
+  CloneTestM2 = CloneTestM0.clone
+  module CloneTestM1
+    TEST = :M1
+  end
+  module CloneTestM2
+    TEST = :M2
+  end
+  class CloneTestC1
+    include CloneTestM1
+  end
+  class CloneTestC2
+    include CloneTestM2
+  end
+
+  def test_constant_access_from_method_in_cloned_module
+    m = CloneTestM_simple.dup
+    assert_equal 1, m::C, '[ruby-core:47834]'
+    assert_equal 1, m.m, '[ruby-core:47834]'
+
+    assert_equal :M1, CloneTestC1.new.foo, '[Bug #15877]'
+    assert_equal :M2, CloneTestC2.new.foo, '[Bug #15877]'
+  end
+
   private
 
   def assert_top_method_is_private(method)