fixes the test for SI-7112

Freshly released Java 1.6.0_41 for OSX fails with "IllegalAccessError:
tried to access class JavaSimpleEnumeration_1 from class sun.proxy.$Proxy6",
and rightfully so, because that class isn't public.

I think I will avoid the usual "how could this even work before" in this
commit message.
Merge pull request #2160 from scalamacros/topic/7112-followup-2101

fixes the test for SI-7112