[autofit] Trace `before' and `after' edges of strong points. * src/autofit/afhints.h (AF_PointRec) [FT_DEBUG_AUTOFIT]: New arrays `before' and `after'. * src/autofit/afhints.c (af_get_strong_edge_index): New auxiliary function. (af_glyph_hints_dump_points): Trace `before' and `after' edges. (af_glyph_hints_align_strong_points) [FT_DEBUG_AUTOFIT]: Set `before' and `after' information.