rm no-updirs because use case is gone, transform to no-parent-or-current-test
That name no-updirs was surprising for me so I spelled it the long way.
remove all case-tolerant methods
Underused and less useful methods don't need to be in the core module -- especially if this could end up in CORE.setting
case-tolerant and default-case-tolerant were split into their own module, File::Spec::Case (for now) where it works almost the same way.