Update Unicode data to Unicode Version 9.0
Unicode 9.0 was just published yesterday (see
Ruby should be updated to this newest version of Unicode.
For details, please see http://unicode.org/versions/Unicode9.0.0/, including http://unicode.org/versions/Unicode9.0.0/#Migration.
[I may use this issue as a summary issue; in that case I'll create sub-issues for particular tasks.]