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.
- cds::lock namespace is renamed to cds::sync. All classes defined in cds::lock namespace
are moved to cds::sync with new names (for example, cds::lock::SpinLock is renamed to
cds::sync::spin_lock). cds::lock namespace and its contents is deprecated, it is kept