Unmark Internal IV test as pending

Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>

ext/-test-/marshal/internal_ivar/internal_ivar.c

@@ -36,10 +36,7 @@ Init_internal_ivar(void)
     VALUE newclass = rb_define_class_under(mMarshal, "InternalIVar", rb_cObject);
 
     id_normal_ivar = rb_intern_const("normal");
-#if 0
-    /* leave id_internal_ivar being 0 */
-    id_internal_ivar = rb_make_internal_id();
-#endif
+    id_internal_ivar = rb_intern_const("K");
     id_encoding_short = rb_intern_const("E");
     rb_define_method(newclass, "initialize", init, 3);
     rb_define_method(newclass, "normal", get_normal, 0);

test/-ext-/marshal/test_internal_ivar.rb

@@ -7,7 +7,6 @@ module Bug end
 module Bug::Marshal
   class TestInternalIVar < Test::Unit::TestCase
     def test_marshal
-      pend "We don't support IVs with ID of 0"
       v = InternalIVar.new("hello", "world", "bye")
       assert_equal("hello", v.normal)
       assert_equal("world", v.internal)