+ - Changed: semantic of member functions extract(), get() and its
+ variants for MichaelList RCU-based specialization: extract() does not
+ require RCU locking, get() now returns special wrapper object of type raw_ptr,
+ see doc.
+ Thus, semantics of extract()/get() of all RCU-based set and maps based on
+ MichaelList (MichaelSet/Map, SplitListSet/Map) has been changed too.
+ - Changed: SplitListSet/Map functions get() and get_with() return special wrapper
+ object of type raw_ptr, see doc.
+ - Removed: SplitListSet/Map force_dispose() function.