Avoid Long.compare(x,y) since it's JDK7+

While clean from an API perspective, this solution creates extra garbage since it has to allocate two Longs to do the comparison. If you're happy with my suggested approach, I'll modify this and merge it:

```
long t1 = c1.getStat().getCtime();
long t2 = c2.getStat().getCtime();
return (t1 < t2) ? -1 : ((t1 == t2) ? 0 : 1);
```