Newer versions of FreeType enable subpixel rendering by default. This makes fonts look terrible on displays that don't support it, like the LCDs this library is targeting. This change disables the subpixel rendering and improves the clarity of fonts.
See https://github.com/adafruit/Adafruit-GFX-Library/issues/103#issuecomment-443031001 for more information.
When compiling the example sketch for adafruit OLED display, the sketch refers to Adafruit_GFX and consequently to fontconvert.c
This file includes a header file named ft2build.h, which many of the compilers fail to find, resulting in compilation error.
Check the discussion on this issue: https://github.com/adafruit/Adafruit-GFX-Library/issues/88
Simply adding two lines solves the problem.
