Using `%ld' for pointer differences causes warnings on 32bit
platforms. The correct type would be (the relatively new) `%td',
however, this is missing on some important platforms.
This patch improves the change from 2014-11-28.
* src/autofit/afhints.c (AF_INDEX_NUM): Use `int' typecast. Our
pointer differences are always sufficiently small.
(af_glyph_hints_dump_points, af_glyph_hints_dump_segments,
af_glyph_hints_dump_edge): Revert to `%d' and use `AF_INDEX_NUM'.