Don't make an exception for NeXT (BBUM says it's no longer needed).

(But hypot() should really be defined in a separate file, triggered by
configure.)

Modules/mathmodule.c

@@ -43,7 +43,7 @@ extern double modf PROTO((double, double *));
 #endif /* _MSC_VER */
 
 
-#if defined(HAVE_HYPOT) && !defined(NeXT)
+#if defined(HAVE_HYPOT)
 extern double hypot PROTO((double, double));
 #else
 double hypot(x,y)