Update build dependencies and edition

Use the 2021 Rust edition. To use current version of clap changes were
adapted.

src/sysv/info.rs

@@ -1,12 +1,12 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use std::{
     fs::File,
     io::{BufRead, BufReader},
 };
 
 /// Print information about an existing message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Info {
     /// Id of the queue
     #[clap(short, long, required_unless_present_any = &["key"], conflicts_with = "key")]