PropertyHandle :: MarkUnused - Mark property handle as unused

When referring a property handle recursively this may result in never deleting the resources allocated with the property handle. Recursive references to property handles may happen when setting transient references (SetTransientProperty()) to an upper property handle. In this case the program has to mark the property handle as unused. Property handles marked as unused must be marked as used before being closed or replaced (CopyHandle()).

Using this function improperly (e.g. after constructing a property handle) may release the resources allocated to the property handle immediately.