vnc: recognize Hungarian doubleacutes

As reported in http://bugs.debian.org/697641

 , some Hungarian keys
does not work with qemu when using vnc display.

This is because while the Hungarian keymap mentions these symbols,
qemu know nothing about them.  So add them.

This patch is applicable to -stable for all previous releases.

Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>