apply simple clippy nightly suggestions

See also:
https://rust-lang.github.io/rust-clippy/master/index.html#manual_contains
https://rust-lang.github.io/rust-clippy/master/index.html#mem_replace_option_with_some
https://rust-lang.github.io/rust-clippy/master/index.html#ptr_eq

Author: BenWiederhake

src/uu/cp/src/copydir.rs

@@ -82,7 +82,7 @@ fn get_local_to_root_parent(
 /// Given an iterator, return all its items except the last.
 fn skip_last<T>(mut iter: impl Iterator<Item = T>) -> impl Iterator<Item = T> {
     let last = iter.next();
-    iter.scan(last, |state, item| std::mem::replace(state, Some(item)))
+    iter.scan(last, |state, item| state.replace(item))
 }
 
 /// Paths that are invariant throughout the traversal when copying a directory.

src/uu/fmt/src/linebreak.rs

@@ -164,9 +164,7 @@ fn break_knuth_plass<'a, T: Clone + Iterator<Item = &'a WordInfo<'a>>>(
 
                 // We find identical breakpoints here by comparing addresses of the references.
                 // This is OK because the backing vector is not mutating once we are linebreaking.
-                let winfo_ptr = winfo as *const _;
-                let next_break_ptr = next_break as *const _;
-                if winfo_ptr == next_break_ptr {
+                if std::ptr::eq(winfo, next_break) {
                     // OK, we found the matching word
                     if break_before {
                         write_newline(args.indent_str, args.ostream)?;

src/uu/unexpand/src/unexpand.rs

@@ -55,7 +55,7 @@ fn tabstops_parse(s: &str) -> Result<Vec<usize>, ParseError> {
         }
     }
 
-    if nums.iter().any(|&n| n == 0) {
+    if nums.contains(&0) {
         return Err(ParseError::TabSizeCannotBeZero);
     }