Where I'm adding my malicious preprocessor macro in Emacs

darwin.h

/* Deleted GPL header - again hopefully RMS won't attack me with a Katana */

/*
 *	Define symbols to identify the version of Unix this is.
 *	Define all the symbols that apply correctly.
 */

#define BSD4_2
/* BSD4_3 and BSD4_4 are already defined in sys/param.h */
#define BSD_SYSTEM

// Sean's changes here

/* More specific than the above two.  We cannot use __APPLE__ as this
   may not be defined on non-OSX Darwin, and we cannot define DARWIN
   here because Panther and lower CoreFoundation.h uses DARWIN to
   distinguish OS X from pure Darwin. */

#define DARWIN_OS