This solves the warnings from -Wredundant-decls when overriding the
  OUTPUT function with a function declared in another header.
 It's better this is the non-default option, since using it requires either
  a declaration of the new function OR a preprocessor guard on declaring
  UNITY_OUTPUT_CHAR (as in unity.c here), in every file using the function.
 See Pull Request #185 for more.