[bdf, pcf] Minor optimization.

* src/pcf/pcfread.c (pcf_load_font): Do not call `FT_MulDiv` for a
small job.
* src/bdf/bdfdrivr.c (BDF_Face_Init): Ditto.
* src/bdf/bdflib.c (_bdf_parse_glyphs): Fix a comment.
3 files changed