Update build dependencies and edition

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

src/sysv/create.rs

@@ -1,10 +1,10 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use log::info;
 use sysvmq::SysvMq;
 
 /// Create a SysV message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Create {
     /// Permissions (octal) to create the queue with (default: 0644)
     #[clap(short, long)]