Implement creation of SysV IPC message queues

This adds the `sysvmq` package which handles SysV IPC message queues.
For consistency the parameter for `permissions` is renamed to `mode`
also for POSIX message queues.

src/main.rs

@@ -2,6 +2,7 @@ use anyhow::Result;
 use clap::{crate_authors, crate_version, AppSettings, Clap};
 
 mod posix;
+mod sysv;
 
 #[derive(Clap, Debug)]
 enum Backend {
@@ -23,6 +24,7 @@ enum PosixCommand {
 
 #[derive(Clap, Debug)]
 enum SysvCommand {
+    Create(sysv::Create),
 }
 
 #[derive(Clap, Debug)]
@@ -65,6 +67,7 @@ fn main() -> Result<()> {
             PosixCommand::Recv(r) => r.run()?,
         },
         Backend::Sysv(s) => match s {
+            SysvCommand::Create(c) => c.run()?,
         },
     }