Lint fixes (#99)

* Replace a single-character string literal with a character literal.

* Use is_some() instead of comparing with Some(_).

* Add code-quotes around type names in comments.

* Use !...is_empty() instead of len() != 0.

* Tidy up redundant returns.

* Remove redundant .clone() calls.

* Remove unnecessary explicit lifetime parameters.

* Tidy up unnecessary '&'s.

* Add parens to make operator precedence explicit.

* Use debug_assert_eq instead of debug_assert with ==.

* Replace a &Vec argument with a &[...].

* Replace `a = a op b` with `a op= b`.

* Avoid unnecessary closures.

* Avoid .iter() and .iter_mut() for iterating over containers.

* Remove unneeded qualification.

lib/reader/src/isaspec.rs

@@ -25,7 +25,7 @@ pub enum IsaSpec {
 impl IsaSpec {
     /// If the `IsaSpec` contains exactly 1 `TargetIsa` we return a reference to it
     pub fn unique_isa(&self) -> Option<&TargetIsa> {
-        if let &IsaSpec::Some(ref isa_vec) = self {
+        if let IsaSpec::Some(ref isa_vec) = *self {
             if isa_vec.len() == 1 {
                 return Some(&*isa_vec[0]);
             }