[smooth] Harmony LCD rendering.

This is a new technology for LCD-optimized rendering. It capitalizes
on the fact that each color channel grid is shifted by a third of a
pixel.  Therefore it is logical to render 3 separate monochrome
bitmaps shifting the outline by 1/3 pixel, and then combine them.
Importantly, the resulting output does not require additional LCD
filtering.

* src/smooth/ftsmooth.c (ft_smooth_render_generic)
[!FT_CONFIG_OPTION_SUBPIXEL_RENDERING]: Implement new LCD-optimized
rendering.

* include/freetype/ftlcdfil.h, include/freetype/freetype.h,
include/freetype/config/ftoption.h, devel/ftoption.h: Updated
documentation.
6 files changed