for an upcoming 2.2.2 release
* include/freetype/ftlcdfil.h, src/freetype/ftlcdfil.c:
added a new API to support color filtering of subpixel glyph
bitmaps. In default build, the function FT_Library_SetLcdFilter
returns FT_Err_Unimplemented_Feature; you need to #define
FT_CONFIG_OPTION_SUBPIXEL_RENDERING in ftoption.h to compile
the real implementation
* src/smooth/ftsmooth.c: adding support for sub-pixel color
filtering; simplifying a few function calls
* include/freetype/config/ftheader.h: adding FT_LCD_FILTER_H
macro that points to <freetype/ftlcdfil.h>