[autofit] Fix crash with font `CabinSketch-Bold.ttf'.

Problem reported by Ralf S. Engelschall <rse@engelschall.com>.

* src/autofit/afhints.c (af_glyph_hints_reload): Fix threshold for
finding first non-near point.
Properly initialize non-near point deltas.
[autofit] Fix variable initializations.

* src/autofit/afhints.c (af_glyph_hints_reload): Assign default
values to `in_dir' and `out_dir' for all points.
* CMakeLists.txt (BASE_SRCS): Add missing `ftbdf.c'.