fix ldexp, frexp, and make math package compile and test correctly

SVN=126423

src/lib/math/log.go

@@ -39,7 +39,7 @@ log(arg double) double
 		return sys.NaN();
 	}
 
-	exp,x = sys.frexp(arg);
+	x,exp = sys.frexp(arg);
 	for x < 0.5 {
 		x = x*2;
 		exp = exp-1;