Update Android port

Update Android port

* configure.ac (HAVE_OTF_GET_VARIATION_GLYPHS): Check for
`hb_font_set_var_named_instance'.
* src/sfnt.c (main): Update tests.
* src/sfntfont-android.c (Fandroid_enumerate_fonts): Blacklist
bad font.
* src/sfntfont.c (struct sfnt_font_tables, struct sfnt_font_desc)
(sfnt_decode_instance_name, sfnt_weight_descriptions)
(sfnt_enum_font_1, sfntfont_list_1, sfntfont_desc_to_entity)
(sfntfont_list, struct sfntfont_get_glyph_outline_dcontext)
(sfntfont_get_glyph, sfntfont_get_glyph_outline)
(struct sfnt_font_info, sfnt_close_tables, sfnt_open_tables)
(sfntfont_open, sfntfont_measure_pcm, sfntfont_close)
(sfntfont_draw, sfntfont_begin_hb_font, syms_of_sfntfont)
(mark_sfntfont): Handle variable fonts correctly.