[HarfBuzz] harfbuzz: Changes to 'coretext-optical-sizing'

[Behdad Esfahbod]

New branch 'coretext-optical-sizing' available with the following commits:
commit a8e466c3c12a3499028cb576721e5f85ff4cbf2d
Author: Behdad Esfahbod <behdad at behdad.org>
Date:   Wed Oct 11 13:05:59 2017 +0200

    [coretext] Move CT_Font to font data
    
    Towards implementing optical sizing.  Untested; won't compile.
    
    https://github.com/behdad/harfbuzz/issues/360

commit f9b4c6570a4725eec5393f86e6468a189ac8c6be
Author: Behdad Esfahbod <behdad at behdad.org>
Date:   Wed Oct 11 12:51:25 2017 +0200

    [coretext] Move font size to a macro