don't use system machine/npx.h on OS X either, since it may not exists and isn't necessary

i387/fenv.c

@@ -29,11 +29,7 @@
 #include <cdefs-compat.h>
 #include <types-compat.h>
 #include <math_private.h>
-#if defined(_WIN32) || defined(__linux__)
 #include <i387/bsd_npx.h>
-#else
-#include <machine/npx.h>
-#endif
 
 #define	__fenv_static
 #include "fenv.h"