make AtomicArc Send/Sync

src/atomic_arc.rs

@@ -11,6 +11,9 @@ pub struct AtomicArc<T> {
     _phantom: PhantomData<Arc<T>>,
 }
 
+unsafe impl<T> Send for AtomicArc<T> where T: Send {} // TODO
+unsafe impl<T> Sync for AtomicArc<T> where T: Sync {} // TODO
+
 impl<T> Drop for AtomicArc<T> {
     fn drop(&mut self) {
         unsafe { Arc::decrement_strong_count(self.load()) }

src/lib.rs

@@ -334,8 +334,6 @@ pub struct Db<R> {
     _phantom: PhantomData<R>,
 }
 
-unsafe impl<R> Send for Db<R> where R: Send {} // TODO
-
 struct SnapshotAndFreeList<R> {
     snapshot: Arc<Snapshot<R>>,
     to_free: Vec<FileRange>,