show --disable-gtk and --enable-gtk in the help message

Signed-off-by: NHu Tao <hutao@cn.fujitsu.com>
Message-id: 1361759268-16314-1-git-send-email-hutao@cn.fujitsu.com
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

configure

@@ -1055,6 +1055,8 @@ echo "  --disable-strip          disable stripping binaries"
 echo "  --disable-werror         disable compilation abort on warning"
 echo "  --disable-sdl            disable SDL"
 echo "  --enable-sdl             enable SDL"
+echo "  --disable-gtk            disable gtk UI"
+echo "  --enable-gtk             enable gtk UI"
 echo "  --disable-virtfs         disable VirtFS"
 echo "  --enable-virtfs          enable VirtFS"
 echo "  --disable-vnc            disable VNC"