Update clippy settings and fix a few clippy warnings.

lib/bforest/src/lib.rs

@@ -17,10 +17,7 @@
 #![warn(unused_import_braces)]
 #![cfg_attr(feature = "std", warn(unstable_features))]
 #![cfg_attr(feature = "clippy", plugin(clippy(conf_file = "../../clippy.toml")))]
-#![cfg_attr(
-    feature = "cargo-clippy",
-    allow(new_without_default, new_without_default_derive)
-)]
+#![cfg_attr(feature = "cargo-clippy", allow(clippy::new_without_default))]
 #![cfg_attr(
     feature = "cargo-clippy",
     warn(

lib/bforest/src/map.rs

@@ -284,7 +284,7 @@ where
     ///
     /// If the cursor reaches the end, return `None` and leave the cursor at the off-the-end
     /// position.
-    #[cfg_attr(feature = "cargo-clippy", allow(should_implement_trait))]
+    #[cfg_attr(feature = "cargo-clippy", allow(clippy::should_implement_trait))]
     pub fn next(&mut self) -> Option<(K, V)> {
         self.path.next(self.pool)
     }

lib/bforest/src/pool.rs

@@ -63,7 +63,7 @@ impl<F: Forest> NodePool<F> {
     pub fn free_tree(&mut self, node: Node) {
         if let NodeData::Inner { size, tree, .. } = self[node] {
             // Note that we have to capture `tree` by value to avoid borrow checker trouble.
-            #[cfg_attr(feature = "cargo-clippy", allow(needless_range_loop))]
+            #[cfg_attr(feature = "cargo-clippy", allow(clippy::needless_range_loop))]
             for i in 0..usize::from(size + 1) {
                 // Recursively free sub-trees. This recursion can never be deeper than `MAX_PATH`,
                 // and since most trees have less than a handful of nodes, it is worthwhile to

lib/bforest/src/set.rs

@@ -225,7 +225,7 @@ where
     ///
     /// If the cursor reaches the end, return `None` and leave the cursor at the off-the-end
     /// position.
-    #[cfg_attr(feature = "cargo-clippy", allow(should_implement_trait))]
+    #[cfg_attr(feature = "cargo-clippy", allow(clippy::should_implement_trait))]
     pub fn next(&mut self) -> Option<K> {
         self.path.next(self.pool).map(|(k, _)| k)
     }