vnc: add a non-adaptive option

This option allow to disable adaptive behaviors in some encodings.

Signed-off-by: Corentin Chary <corentincj@iksaif.net>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
diff --git a/ui/vnc.h b/ui/vnc.h
index 98a1885..8a1e7b9 100644
--- a/ui/vnc.h
+++ b/ui/vnc.h
@@ -144,6 +144,7 @@
     time_t expires;
     int auth;
     bool lossy;
+    bool non_adaptive;
 #ifdef CONFIG_VNC_TLS
     int subauth; /* Used by VeNCrypt */
     VncDisplayTLS tls;