tor-netdoc: Make SectionRules derive Clone.

This is going to come in handy for the networkstatus stuff, where I
need to define different variants of SectionRules for votes and
consensuses.

tor-netdoc/src/parse.rs

@@ -22,6 +22,7 @@ use crate::{Error, Result};
 ///
 /// The rules are represented as a mapping from token index to
 /// rules::TokenFmt.
+#[derive(Clone)]
 pub struct SectionRules<T: Keyword> {
     rules: Vec<Option<TokenFmt<T>>>,
 }