Basic support for QEMU Extended Key Events

This adds the basic infrastructure and handshake for the QEMU
Extended Key Events extension. No viewer or server makes use of
the extra functionality yet though.
diff --git a/win/rfb_win32/SDisplay.cxx b/win/rfb_win32/SDisplay.cxx
index 2696f5d..ad55d49 100644
--- a/win/rfb_win32/SDisplay.cxx
+++ b/win/rfb_win32/SDisplay.cxx
@@ -280,12 +280,12 @@
   }
 }
 
-void SDisplay::keyEvent(rdr::U32 key, bool down) {
+void SDisplay::keyEvent(rdr::U32 keysym, rdr::U32 keycode, bool down) {
   // - Check that the SDesktop doesn't need restarting
   if (isRestartRequired())
     restartCore();
   if (kbd)
-    kbd->keyEvent(key, down);
+    kbd->keyEvent(keysym, keycode, down);
 }
 
 bool SDisplay::checkLedState() {