Resize state machine: A fix and a question (#2929)

* Store EGFX state before entering resize state machine

At present the EGFX state is destroyed by states WMRZ_EGFX_DELETE_SURFACE
through WRMZ_EGFX_DELETE. This means that at WMRZ_EGFX_INITIALIZE we
cannot distinguish between EGFX not being ever used, and EGFX
having been torn down. Consequently, when running non-GFX, we don't
correctly recover the session.

* Allow multiple reasons for suppress_output

Replaces the single boolean for suppress_output with
a bitmask, to allow output to be suppressed for
more than one reason

* Disable output during resize

* Add states to dynamic resize

Adds states to the dynamic resize state machine so we wait for a
Deactivation-Reactivation sequence to finish before sending pointer
updates, etc.

* suppress module output during the dynamic resize

* Add support for dynamic resize to VNC backend

xrdp_mm needs to be informed when a resize has been performed so that
the resize stte machine can be updsate.

libxrdp/libxrdp.c

@@ -1181,6 +1181,12 @@ libxrdp_reset(struct xrdp_session *session,
         return 1;
     }
 
+    /*
+     * Stop output from the client during the deactivation-reactivation
+     * sequence [MS-RDPBCGR] 1.3.1.3 */
+    xrdp_rdp_suppress_output((struct xrdp_rdp *)session->rdp, 1,
+                             XSO_REASON_DEACTIVATE_REACTIVATE, 0, 0, 0, 0);
+
     /* shut down the rdp client
      *
      * When resetting the lib, disable application input checks, as