qapi: Generalize command policy checking

The code to check command policy can see special feature flag
'deprecated' as command flag QCO_DEPRECATED.  I want to make feature
flag 'unstable' visible there as well, so I can add policy for it.

To let me make it visible, add member @special_features (a bitset of
QapiSpecialFeature) to QmpCommand, and adjust the generator to pass it
through qmp_register_command().  Then replace "QCO_DEPRECATED in
@flags" by QAPI_DEPRECATED in @special_features", and drop
QCO_DEPRECATED.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Acked-by: John Snow <jsnow@redhat.com>
Message-Id: <20211028102520.747396-7-armbru@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
diff --git a/monitor/misc.c b/monitor/misc.c
index 3556b17..c2d227a 100644
--- a/monitor/misc.c
+++ b/monitor/misc.c
@@ -230,11 +230,13 @@
 
     qmp_init_marshal(&qmp_commands);
 
-    qmp_register_command(&qmp_commands, "device_add", qmp_device_add, 0);
+    qmp_register_command(&qmp_commands, "device_add",
+                         qmp_device_add, 0, 0);
 
     QTAILQ_INIT(&qmp_cap_negotiation_commands);
     qmp_register_command(&qmp_cap_negotiation_commands, "qmp_capabilities",
-                         qmp_marshal_qmp_capabilities, QCO_ALLOW_PRECONFIG);
+                         qmp_marshal_qmp_capabilities,
+                         QCO_ALLOW_PRECONFIG, 0);
 }
 
 /* Set the current CPU defined by the user. Callers must hold BQL. */