Use clippy (#276)

* cton-util: fix some clippy unnecessary pass-by-value warnings

* clippy: ignore too many arguments / cyclomatic complexity in module

since these functions are taking args coming from the command line, i
dont think this is actually a valid lint, morally the arguments are all
from one structure

* cton-util: take care of remaining clippy warnings

* cton-reader: fix all non-suspicious clippy warnings

* cton-reader: disable clippy at site of suspicious lint

* cton-frontend: disable clippy at the site of an invalid lint

* cton-frontend: fix clippy warnings, or ignore benign ones

* clippy: ignore the camelcase word WebAssembly in docs

* cton-wasm: fix clippy complaints or ignore benign ones

* cton-wasm tests: fix clippy complaints

* cretonne: starting point turns off all clippy warnings

* cretonne: clippy fixes, or lower allow() to source of problem

* cretonne: more clippy fixes

* cretonne: fix or disable needless_lifetimes lint

this linter is buggy when the declared lifetime is used for another type
constraint.

* cretonne: fix clippy complaint about Pass::NoPass

* rustfmt

* fix prev minor api changes clippy suggested

* add clippy to test-all

* cton-filetests: clippy fixes

* simplify clippy reporting in test-all

* cretonne: document clippy allows better

* cretonne: fix some more clippy lints

* cretonne: fix clippy lints (mostly doc comments)

* cretonne: allow all needless_lifetimes clippy warnings

remove overrides at the false positives

* rustfmt

lib/cretonne/src/print_errors.rs

@@ -10,7 +10,7 @@ use std::fmt::Write;
 pub fn pretty_verifier_error(
     func: &ir::Function,
     isa: Option<&TargetIsa>,
-    err: verifier::Error,
+    err: &verifier::Error,
 ) -> String {
     let mut msg = err.to_string();
     match err.location {
@@ -26,7 +26,7 @@ pub fn pretty_verifier_error(
 /// Pretty-print a Cretonne error.
 pub fn pretty_error(func: &ir::Function, isa: Option<&TargetIsa>, err: CtonError) -> String {
     if let CtonError::Verifier(e) = err {
-        pretty_verifier_error(func, isa, e)
+        pretty_verifier_error(func, isa, &e)
     } else {
         err.to_string()
     }