6692899: CMS: many vm.parallel_class_loading tests fail with assert "missing Printezis mark"
Summary: The CMS concurrent precleaning and concurrent marking phases should work around classes that are undergoing redefinition.
Reviewed-by: ysr, dcubed
6689653: JMapPerm fails with UseConcMarkSweepIncGC and compressed oops off
Summary: Added safe_object_iterate() for use by JMapPerm.
Reviewed-by: tonyp