[raster] Handle `FT_RASTER_FLAG_AA' correctly.

This fixes a breakage caused by the commit `[raster] Remove
5-level gray AA mode from monochrome rasterizer.'.

Problem reported by Markus Trippelsdorf <markus@trippelsdorf.de> and
octoploid <octoploid@yandex.com>.

* src/raster/ftraster.c (ft_black_render): Handle
`FT_RASTER_FLAG_AA'.

* src/raster/ftrend1.c (ft_raster1_render): Remove gray AA mode
remnants.
3 files changed