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

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
Message-id: 1361759268-16314-1-git-send-email-hutao@cn.fujitsu.com
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/configure b/configure
index 8b6309f..19738ac 100755
--- a/configure
+++ b/configure
@@ -1055,6 +1055,8 @@
 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"