Merge pull request #18 from vog/improve-layouter-font-interface

Cleanup interface of fontFace_c: Reduce FT dependencies to a minimum
Cleanup interface of freeTypeLibrary_c: Reduce FT dependencies to a minimum
Cleanup interface of textLayout_c: Make type of glyphIndex independent from FT

This needs a cast for PugiXML because PugiXML has no propert support
for long ints.