Fix clippy warnings.

This commit fixes the current set of (stable) clippy warnings in the repo.

cranelift/codegen/shared/src/constant_hash.rs

@@ -24,6 +24,7 @@ pub fn simple_hash(s: &str) -> usize {
 /// Compute an open addressed, quadratically probed hash table containing
 /// `items`. The returned table is a list containing the elements of the
 /// iterable `items` and `None` in unused slots.
+#[allow(clippy::float_arithmetic)]
 pub fn generate_table<'cont, T, I: iter::Iterator<Item = &'cont T>, H: Fn(&T) -> usize>(
     items: I,
     num_items: usize,