Merge branch 'bb/unicode-9.0' into maint

The character width table has been updated to match Unicode 9.0

* bb/unicode-9.0:
  unicode_width.h: update the width tables to Unicode 9.0
  update_unicode.sh: remove the plane filter
  update_unicode.sh: automatically download newer definition files
  update_unicode.sh: pin the uniset repo to a known good commit
  update_unicode.sh: remove an unnecessary subshell level
  update_unicode.sh: move it into contrib/update-unicode

diff --cc .gitignore
Simple merge