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/preopt.rs

@@ -114,7 +114,7 @@ fn package_up_divrem_info(
 fn get_div_info(inst: Inst, dfg: &DataFlowGraph) -> Option<DivRemByConstInfo> {
     let idata: &InstructionData = &dfg[inst];
 
-    if let &InstructionData::BinaryImm { opcode, arg, imm } = idata {
+    if let InstructionData::BinaryImm { opcode, arg, imm } = *idata {
         let (isSigned, isRem) = match opcode {
             Opcode::UdivImm => (false, false),
             Opcode::UremImm => (false, true),
@@ -132,7 +132,7 @@ fn get_div_info(inst: Inst, dfg: &DataFlowGraph) -> Option<DivRemByConstInfo> {
     // that some previous constant propagation pass has pushed all such
     // immediates to their use points, creating BinaryImm instructions
     // instead? For now we take the conservative approach.
-    if let &InstructionData::Binary { opcode, args } = idata {
+    if let InstructionData::Binary { opcode, args } = *idata {
         let (isSigned, isRem) = match opcode {
             Opcode::Udiv => (false, false),
             Opcode::Urem => (false, true),
@@ -484,7 +484,7 @@ fn get_const(value: Value, dfg: &DataFlowGraph) -> Option<i64> {
     match dfg.value_def(value) {
         ValueDef::Result(definingInst, resultNo) => {
             let definingIData: &InstructionData = &dfg[definingInst];
-            if let &InstructionData::UnaryImm { opcode, imm } = definingIData {
+            if let InstructionData::UnaryImm { opcode, imm } = *definingIData {
                 if opcode == Opcode::Iconst && resultNo == 0 {
                     return Some(imm.into());
                 }