Log Message:
Updated harfbuzz to 1.2.7.

Overview of changes leading to 1.2.7
Monday, May 2, 2016
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- Blacklist another version of Times New Roman (Bold) Italic from Windows 7.
- Fix Mongolian Free Variation Selectors shaping with certain fonts.
- Fix Tibetan shorthand contractions shaping.
- Improved list of language tag mappings.
- Unbreak build on Windows CE.
- Make 'glyf' table loading lazy in hb-ot-font.