This is mostly cosmetic and removes a few casts, plus Short is
promoted to Int in calculations anyway.
* src/raster/ftraster.c (Vertical_Sweep_Init, Vertical_Sweep_Span,
Vertical_Sweep_Drop, Horizontal_Sweep_Init, Horizontal_Sweep_Span,
Horizontal_Sweep_Drop, Draw_Sweep): Mostly s/Short/Int/ and remove
casting.