Introduce a WindowProxy for accessing a subset of functionality

from other threads. This currently provides a way for other threads
to wakeup a blocked event loop on X11. Other platforms have stub
functions that need to be implemented. This is similar to
the functionality of glfwPostEmptyEvent.

src/win32/mod.rs

@@ -83,6 +83,16 @@ impl Window {
     }
 }
 
+#[cfg(feature = "window")]
+#[deriving(Clone)]
+pub struct WindowProxy;
+
+impl WindowProxy {
+    pub fn wakeup_event_loop(&self) {
+        // TODO
+    }
+}
+
 impl Window {
     /// See the docs in the crate root file.
     pub fn is_closed(&self) -> bool {
@@ -180,6 +190,10 @@ impl Window {
         }
     }
 
+    pub fn create_window_proxy(&self) -> WindowProxy {
+        WindowProxy
+    }
+
     /// See the docs in the crate root file.
     // TODO: return iterator
     pub fn poll_events(&self) -> Vec<Event> {