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/common/rfb/VNCSConnectionST.h b/common/rfb/VNCSConnectionST.h
index 8f33962..9c58331 100644
--- a/common/rfb/VNCSConnectionST.h
+++ b/common/rfb/VNCSConnectionST.h
@@ -136,7 +136,7 @@
     virtual void clientInit(bool shared);
     virtual void setPixelFormat(const PixelFormat& pf);
     virtual void pointerEvent(const Point& pos, int buttonMask);
-    virtual void keyEvent(rdr::U32 key, bool down);
+    virtual void keyEvent(rdr::U32 keysym, rdr::U32 keycode, bool down);
     virtual void clientCutText(const char* str, int len);
     virtual void framebufferUpdateRequest(const Rect& r, bool incremental);
     virtual void setDesktopSize(int fb_width, int fb_height,