[Lucene-java Wiki] Update of "ReleaseNote64" by MikeMcCandless

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The "ReleaseNote64" page has been changed by MikeMcCandless:
https://wiki.apache.org/lucene-java/ReleaseNote64?action=diff&rev1=10&rev2=11

  Lucene 6.4.0 Release Highlights:
  
  New features
+  * Lucene's best efforts to un-map memory mapped files with "!MMapDirectory" now work with the latest Java9 early access builds
-  * A new similarity "!BooleanSimilarity that gives terms a score that is equal to their query boost
+  * A new similarity "!BooleanSimilarity" that gives terms a score that is equal to their query boost
+  * The axiomatic family of similarities (6 in total) based on https://www.eecis.udel.edu/~hfang/pubs/sigir05-axiom.pdf
   * A new analyzer "!SynonymGraphFilter" that outputs a correct graph structure for multi-token synonyms at query time
   * Graph token streams produced by the "!SynonymGraphFilter" are now handled accurately by query parsers
   * A new collector "!DocValuesStatsCollector" gives the ability to compute statistics on DocValues field
   * It is now possible to filter "!SortedDocValues" and "!SortedSetDocValues" terms enum with a compiled automaton
   * The "!UnifiedHighlighter" can now highlight fields with queries that don't necessarily refer to that field
   * DrillSideways can now run queries concurrently
+  * Index sorting now supports sorting on multi-valued fields using MIN, MAX, etc. selectors
  
  Optimizations
   * Points do not store the implicit split dimension in the 1-dimension case. This saves between 6% memory for the largest types such an !InetAddressPoint to 33% for the smaller types such as !HalfFloatPoint.
   * The BKD in-memory index for dimensional points now uses a compressed format, using substantially less RAM in some cases
   * The BKD writing now buffers each leaf block in heap before writing to disk, giving a small speedup in points-heavy use cases
+  * "!TermAutomatonQuery" now rewrites to more efficient queries when possible
+  * Index sorting now sorts on flush instead of first merge, resulting in sizable speedups: see annotation V in https://home.apache.org/~mikemccand/lucenebench/sparseResults.html#index_throughput
  
  Along with numerous bug fixes.