magic comment test only if encoding_aware?.

activerecord/test/cases/schema_dumper_test.rb

@@ -14,9 +14,10 @@ def standard_dump
     @stream.string
   end
 
-  def test_magic_comment
-    skip "only test magic comments on 1.9" if RUBY_VERSION < '1.9'
-    assert_match "# encoding: #{@stream.external_encoding.name}", standard_dump
+  if "string".encoding_aware?
+    def test_magic_comment
+      assert_match "# encoding: #{@stream.external_encoding.name}", standard_dump
+    end
   end
 
   def test_schema_dump