Read linegap from TrueType fonts
Recursively resolve composite glyphs for TrueType fonts.

Some fonts have composite glyphs that reference other composite glyphs, HPDF
wouldn't embed the glyphs referenced from them in the generated PDF file.

Affects e.g. the *dieresis-glyphs in FreeSans:
* Adieresis: composite glyph, A and dieresis
* dieresis: composite glyph - two times dotaccent