Update build dependencies and edition

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

src/main.rs

@@ -1,10 +1,10 @@
 use anyhow::Result;
-use clap::{crate_authors, crate_version, AppSettings, Clap};
+use clap::{crate_authors, crate_version, AppSettings, Parser};
 
 mod posix;
 mod sysv;
 
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 enum Backend {
     /// Handle POSIX message queues
     #[clap(subcommand)]
@@ -14,7 +14,7 @@ enum Backend {
     Sysv(SysvCommand),
 }
 
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 enum PosixCommand {
     Create(posix::Create),
     Info(posix::Info),
@@ -24,7 +24,7 @@ enum PosixCommand {
     Recv(posix::Recv),
 }
 
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 enum SysvCommand {
     Create(sysv::Create),
     Info(sysv::Info),
@@ -32,7 +32,7 @@ enum SysvCommand {
     Unlink(sysv::Unlink),
 }
 
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 #[clap(
     version = crate_version!(),
     author = crate_authors!(", "),

src/posix/create.rs

@@ -1,11 +1,11 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use log::{info, log_enabled, Level::Info};
 use posixmq::PosixMq;
 use std::fs;
 
 /// Create a POSIX message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Create {
     /// Permissions (octal) to create the queue with
     #[clap(short, long)]

src/posix/info.rs

@@ -1,9 +1,9 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use posixmq::PosixMq;
 
 /// Print information about an existing message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Info {
     /// Name of the queue
     #[clap(value_name = "QUEUE")]

src/posix/list.rs

@@ -1,11 +1,11 @@
 use anyhow::{anyhow, Result};
 use chrono::{DateTime, Local};
-use clap::Clap;
+use clap::Parser;
 use log::warn;
 use std::{fs, os::unix::fs::PermissionsExt};
 
 /// Print a list of existing message queues
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct List {
     /// Show all parameters
     #[clap(short, long)]

src/posix/recv.rs

@@ -1,13 +1,13 @@
 use anyhow::Result;
 use chrono::{DateTime, Local};
-use clap::Clap;
+use clap::Parser;
 use humantime::Duration;
 use log::info;
 use posixmq::PosixMq;
 use std::str;
 
 /// Receive and print a message from a message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Recv {
     /// Do not block
     #[clap(short, long)]

src/posix/send.rs

@@ -1,11 +1,11 @@
 use anyhow::Result;
 use chrono::DateTime;
-use clap::Clap;
+use clap::Parser;
 use humantime::Duration;
 use log::info;
 
 /// Send a message to a message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Send {
     /// Set a different priority, priority >= 0
     #[clap(short, long, default_value = "0")]

src/posix/unlink.rs

@@ -1,9 +1,9 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use log::info;
 
 /// Delete a message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Unlink {
     /// Name of the queue
     #[clap(value_name = "QUEUE")]

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)]

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")]

src/sysv/list.rs

@@ -1,12 +1,12 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use std::{
     fs::File,
     io::{BufRead, BufReader},
 };
 
 /// Print a list of existing message queues
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct List {}
 
 impl List {

src/sysv/unlink.rs

@@ -1,9 +1,9 @@
 use anyhow::Result;
-use clap::Clap;
+use clap::Parser;
 use log::info;
 
 /// Delete a message queue
-#[derive(Clap, Debug)]
+#[derive(Debug, Parser)]
 pub struct Unlink {
     /// Id of the queue
     #[clap(