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/frontend/src/frontend.rs

@@ -400,7 +400,7 @@ where
     ///
     /// This can be used to insert SSA code that doesn't need to access locals and that doesn't
     /// need to know about `FunctionBuilder` at all.
-    pub fn cursor<'f>(&'f mut self) -> FuncCursor<'f> {
+    pub fn cursor(&mut self) -> FuncCursor {
         self.ensure_inserted_ebb();
         FuncCursor::new(self.func)
             .with_srcloc(self.srcloc)
@@ -548,6 +548,8 @@ where
     /// Returns a displayable object for the function as it is.
     ///
     /// Useful for debug purposes. Use it with `None` for standard printing.
+    // Clippy thinks the lifetime that follows is needless, but rustc needs it
+    #[cfg_attr(feature = "cargo-clippy", allow(needless_lifetimes))]
     pub fn display<'b, I: Into<Option<&'b TargetIsa>>>(&'b self, isa: I) -> DisplayFunction {
         self.func.display(isa)
     }