/// Finds \p key and return the item found
/** \anchor cds_nonintrusive_MichaelHashMap_rcu_get
The function searches the item with key equal to \p key and returns the pointer to item found.
- If \p key is not found it returns \p NULL.
+ If \p key is not found it returns \p nullptr.
Note the compare functor should accept a parameter of type \p K that can be not the same as \p key_type.