Auto merge of #21932 - Jormundir:std-os-errno-type, r=alexcrichton

Changes std::os::errno to return i32, the return type used by the function being delegated to.

This is my first contribution, so feel free to give me advice. I'll be happy to correct things.

src/libstd/sys/unix/process.rs

@@ -394,7 +394,7 @@ impl Process {
                 match unsafe { c::select(max, &mut set, ptr::null_mut(),
                                          ptr::null_mut(), p) } {
                     // interrupted, retry
-                    -1 if os::errno() == libc::EINTR as uint => continue,
+                    -1 if os::errno() == libc::EINTR as i32 => continue,
 
                     // We read something, break out and process
                     1 | 2 => {}

src/libstd/sys/unix/timer.rs

@@ -198,7 +198,7 @@ fn helper(input: libc::c_int, messages: Receiver<Req>, _: ()) {
                 assert_eq!(fd.read(&mut buf).ok().unwrap(), 1);
             }
 
-            -1 if os::errno() == libc::EINTR as uint => {}
+            -1 if os::errno() == libc::EINTR as i32 => {}
             n => panic!("helper thread failed in select() with error: {} ({})",
                        n, os::last_os_error())
         }