• Merge pull request #318 from spyridon97/improve-build-multithreading
  Rewrite nanoflann's concurrent index build
  At 16 threads, index build time drops ~3.5x on uniform data
  (79ms -> 23ms) and ~3.8x on clustered data (108ms -> 29ms).
• Merge pull request #317 from jschueller/mtune
  CMake: Check for mtune=native flag
  For some archs like ppc64 this is not always available
• Merge pull request #315 from jlblancoc/fix/unsigned-elementtype-crash
  Fix crash and wrong results with unsigned ElementType (alternative to #314)
• fix: compute all coordinate differences in DistanceType
• Contributors: Jose Luis Blanco-Claraco, Julien Schueller, Spiros Tsalikis