Fixed a bug that returned an invalid linear width for composite
TrueType glyphs.
* include/internal/tttypes.h (TT_Loader_): Two new elements `linear'
and `linear_def'.
* src/truetype/ttgload.c (load_truetype_glyph,
compute_glyph_metrics): Use it.
* include/fttypes.h (FT_ERROR_BASE): New macro.
* src/base/ftobjs.c (FT_Open_Face, FT_Render_Glyph_Internal): Use it
to make source code work with the new error scheme implemented by
Werner.
* src/base/ftoutln.c (FT_Outline_Render): Ditto.