[HarfBuzz] Where hb_glyph_buffer_* functions are implemented?

[Vyacheslav Karamov]

Hi All!

I found declarations of hb_glyph_buffer_new(size_t item_size) and other 
hb_glyph_buffer_* functions, but I can't find usage and implementation.
A they obsolete?

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WBR,
Vyacheslav.