[cairo] how to clear the freetype face cache?

[Cosmin Apreutesei]

Hi,

When my app closes I need to FT_Done_Face on all used faces so I can
FT_Done_Freetype, otherwise I get a crash. But cairo still holds
multiple references to each cairo_font_face_t created with
cairo_ft_font_face_create_for_ft_face (one for every seleted size as I
can see) and the doc says I shouldn't FT_Done_Face until those
references are gone.

So my question is: is there any way to tell cairo to clear its font
cache and release those cairo_font_face_t objects?

Thanks,
Cosmin.