Log Message:
harfbuzz: update to 1.8.7.

Overview of changes leading to 1.8.7
Wednesday, August 8, 2018
====================================
- Fix assertion failure with GDEF-blacklisted fonts.

Overview of changes leading to 1.8.6
Tuesday, August 7, 2018
====================================
- Internal code shuffling.
- New API to speed up getting advance widths for implementations
  that have heavy overhead in get_h_advance callback:
+hb_font_funcs_set_glyph_h_advances_func
+hb_font_funcs_set_glyph_v_advances_func
+hb_font_get_glyph_advances_for_direction
+hb_font_get_glyph_h_advances
+hb_font_get_glyph_h_advances_func_t
+hb_font_get_glyph_v_advances
+hb_font_get_glyph_v_advances_func_t

Overview of changes leading to 1.8.5
Wednesday, August 1, 2018
====================================
- Major Khmer shaper improvements to better match Microsoft.
- Indic bug fixes.
- Internal improvements to atomic operations.

Overview of changes leading to 1.8.4
Tuesday, July 17, 2018
====================================
- Fix build on non-C++11.
- Use C++-style GCC atomics and C++11 atomics.

Overview of changes leading to 1.8.3
Wednesday, July 11, 2018
====================================
- A couple of Indic / USE bug fixes.
- Disable vectorization, as it was causing unaligned access bus error on
  certain 32bit architectures.

Overview of changes leading to 1.8.2
Tuesday, July 3, 2018
====================================
- Fix infinite loop in Khmer shaper.
- Improve hb_blob_create_from_file() for streams.