VNC: Support for ExtendedKeyEvent client message

VNC: Support for ExtendedKeyEvent client message

This patch adds support for the ExtendedKeyEvent client message.  This message
allows a client to send raw scan codes directly to the server.  If the client
and server are using the same keymap, then it's unnecessary to use the '-k'
option with QEMU when this extension is supported.

This is extension is currently only implemented by gtk-vnc based clients
(gvncviewer, virt-manager, vinagre, etc.).

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5076 c046a42c-6fe2-441c-8c8c-71466251a162