Fix all clippy warnings (#564)

* Fix all clippy warnings

* Revert usage of inclusive ranges

* Remove redundant function argument

* Revert use of unavailable pointer methods

* Introduce ContiguousCaseRange

cranelift/src/compile.rs

@@ -151,7 +151,7 @@ fn handle_module(
 }
 
 fn print_readonly_data(mem: &[u8]) {
-    if mem.len() == 0 {
+    if mem.is_empty() {
         return;
     }