clippy: fix a couple nits

Running `cargo +nightly clippy --all-features` finds a couple things in
the compiler. Fix these. One is a subtle change to our `OrdF64` type:
this is a wrapper type to add `Ord` to f64, panicking in the case that
we hit NaN.

Previously our `Ord` impl would panic but our `PartialOrd` impl would
not. Now they both do.

Author: apoelstra

src/policy/compiler.rs

@@ -31,7 +31,7 @@ impl Eq for OrdF64 {}
 // We could derive PartialOrd, but we can't derive Ord, and clippy wants us
 // to derive both or neither. Better to be explicit.
 impl PartialOrd for OrdF64 {
-    fn partial_cmp(&self, other: &OrdF64) -> Option<cmp::Ordering> { self.0.partial_cmp(&other.0) }
+    fn partial_cmp(&self, other: &OrdF64) -> Option<cmp::Ordering> { Some(self.cmp(other)) }
 }
 impl Ord for OrdF64 {
     fn cmp(&self, other: &OrdF64) -> cmp::Ordering {

src/policy/concrete.rs

@@ -1093,7 +1093,7 @@ fn with_huffman_tree<Pk: MiniscriptKey>(
 /// any one of the conditions exclusively.
 #[cfg(feature = "compiler")]
 fn generate_combination<Pk: MiniscriptKey>(
-    policy_vec: &Vec<Arc<Policy<Pk>>>,
+    policy_vec: &[Arc<Policy<Pk>>],
     prob: f64,
     k: usize,
 ) -> Vec<(f64, Arc<Policy<Pk>>)> {