[HarfBuzz] bug in `hb_ot_layout_lookup_collect_lookups'

[Werner LEMBERG]

> However, I see that the mapping result of lookup 76, `glyph242', is
> part of the set returned by `hb_ot_layout_lookup_collect_glyphs', so
> everything's' fine.  Sorry for the noise.

Well, I've now taken a look at `mangal.ttf' (version 5.91 from
Windows 7), and I get *a lot* of glyphs not covered by
`hb_ot_layout_lookup_collect_glyphs', which is really bad for me.

Example: `glyph201', which is part of the following rule in lookup 7:

  <LigatureSet glyph="uni0915">
     <Ligature components="uni094D" glyph="glyph201"/>

It is also part of lookup 11:

  <LigatureSet glyph="glyph201">
    <Ligature components="glyph90" glyph="glyph345"/>

and lookup 15:

  <LigatureSet glyph="glyph201">
    <Ligature components="uni0924" glyph="glyph417"/>


    Werner


PS: Note that there are also some glyphs in the font (like `glyph54')
    that are used as subglyphs in composite glyphs only – something I
    have to take care directly in ttfautohint –, but the above problem
    is independent of that, since subglyphs and ligatures are two
    different issues.