qxl: require spice >= 0.8.2

drop all ifdefs on SPICE_INTERFACE_QXL_MINOR >= 1 as a result,
any check for SPICE_SERVER_VERSION that is now always satisfied,
and SPICE_INTERFACE_CORE_MINOR >= 3 tests, because
0.8.2 has SPICE_INTERFACE_QXL_MINOR == 1 and
SPICE_INTERFACE_CORE_MINOR == 3.

Signed-off-by: Alon Levy <alevy@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
