These are put in their own crate so that we can link tests against libwings freely.

Once libwings is entirely rewritten in Rust, we should be able to move these tests back into the wings-rs crate.

@@ -0,0 +26,4 @@
+impl Lock {
+    pub(crate) fn new(display: u16, file: File) -> Result<Self, LockError> {
+        match file.try_lock() {
+            Ok(_) => return Ok(Lock { display, file }),

@@ -0,0 +74,4 @@
+    /// `/tmp/.X*-lock`. If such a file exists, its `DISPLAY` value will not be
+    /// used.
+    ///
+    /// Note also that this approach is far from perfect (and prone to TOCTOU

@@ -0,0 +86,4 @@
+                return None;
+            }
+            let next = prev + 1;
+            if let Ok(exists) = fs::exists(Path::new(&format!("/tmp/.X{}-lock", next))) && exists {

@@ -0,0 +42,4 @@
+    fn drop(&mut self) {
+        // `file` should be unlocked on drop, but we explicitly unlock it and
+        // unwrap the result so that errors aren't dropped silently.
+        self.file.unlock().expect("could not unlock file");