Requiring spice-server >= 0.8.2 is not enough since spice-server.pc
doesn't require spice-protocol (any version). Until that is fixed
upstream an explicit requirement in qemu fixes compilation broken since

commit 2e1a98c9
Author: Alon Levy <alevy@redhat.com>
Date:   Fri Feb 24 23:19:30 2012 +0200

    qxl: introduce QXLCookie
Reported-by: NPeter Maydell <peter.maydell@linaro.org>
Signed-off-by: NAlon Levy <alevy@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>