Auto merge of #8355 - Jarcho:explicit_auto_deref_2, r=flip1995

Add lint `explicit_auto_deref` take 2

fixes: #234
fixes: #8367
fixes: #8380

Still things to do:

* ~~This currently only lints `&*<expr>` when it doesn't trigger `needless_borrow`.~~
* ~~This requires a borrow after a deref to trigger. So `*<expr>` changing `&&T` to `&T` won't be caught.~~
* The `deref` and `deref_mut` trait methods aren't linted.
* Neither ~~field accesses~~, nor method receivers are linted.
* ~~This probably shouldn't lint reborrowing.~~
* Full slicing to deref should probably be handled here as well. e.g. `&vec[..]` when just `&vec` would do

changelog: new lint `explicit_auto_deref`

CHANGELOG.md

@@ -3400,6 +3400,7 @@ Released 2018-09-13
 [`expect_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_fun_call
 [`expect_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_used
 [`expl_impl_clone_on_copy`]: https://rust-lang.github.io/rust-clippy/master/index.html#expl_impl_clone_on_copy
+[`explicit_auto_deref`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_auto_deref
 [`explicit_counter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_counter_loop
 [`explicit_deref_methods`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_deref_methods
 [`explicit_into_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_into_iter_loop

clippy_dev/src/update_lints.rs

@@ -413,7 +413,7 @@ fn remove_lint_declaration(name: &str, path: &Path, lints: &mut Vec<Lint>) -> io
                 .find("declare_lint_pass!")
                 .unwrap_or_else(|| panic!("failed to find `impl_lint_pass`"))
         });
-        let mut impl_lint_pass_end = (&content[impl_lint_pass_start..])
+        let mut impl_lint_pass_end = content[impl_lint_pass_start..]
             .find(']')
             .expect("failed to find `impl_lint_pass` terminator");