Update for changes in Send/Sync traits

src/x11/headless.rs

@@ -62,3 +62,6 @@ impl Drop for HeadlessContext {
         unsafe { ffi::OSMesaDestroyContext(self.context) }
     }
 }
+
+unsafe impl Send for HeadlessContext {}
+unsafe impl Sync for HeadlessContext {}

src/x11/window/mod.rs

@@ -34,6 +34,9 @@ struct XWindow {
     im: ffi::XIM,
 }
 
+unsafe impl Send for Window {}
+unsafe impl Sync for Window {}
+
 impl Drop for XWindow {
     fn drop(&mut self) {
         unsafe {