SHM IPC example in Rust

This is an example implementatation of synchronized queue for inter-process communication in shared memory
for UNIX POSIX-complaint operating systems.

Motivation is to try out rust in unix systems programming

Goals:

• Safe IPC queue implementation
• Rusty wrappers for pthread sync primitives

Non-goals:

• Fast IPC queue
• Production-ready code
• Full-featured wrappers

Library support

Currently this example relies on master branch of rust-lang/libc because of
https://github.com/rust-lang/libc/commit/532d80cdc139ea56351e21685bcfba2d3c93e34d

Required bindings will be availible in version 0.2.21

Usage example

fn child(queue: Shm<Queue<i32>>) {
    let pid = process::pid();
    queue.push(pid).unwrap()
}
fn main() {    
    // Create new queue in shm
    let queue = Shm::new(Queue::pshared())
        .unwrap();
    // Spawn processes
    for _ in 0..10 {
        process::spawn(|| {
            child(queue.clone());
        }).unwrap();    
    }
    while let Ok(Some(pid)) = queue.timed_pop(Duration::from_millis(10)) {
        println!("PID {}", pid);
    }   
}