A basic justification algorithm for HarfBuzz-NG

This does mostly the same HB-old did, except of non-BMP codepoints
support and better handling of space and punctuation characters.

Change-Id: Iaf8565a35f27d5f4837128cec345eff3d9d2bdf0
Reviewed-by: Lars Knoll <lars.knoll@digia.com>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>