monitor: Add user_print() to mon_cmd_t

This new struct member will store a pointer to a function that
should be used to output data in the user protocol format.

It will also serve as a flag to say if a given handler has already
been converted to the new QObject style.

Patchworks-ID: 35339
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

monitor.c

@@ -73,6 +73,7 @@ typedef struct mon_cmd_t {
     const char *args_type;
     const char *params;
     const char *help;
+    void (*user_print)(Monitor *mon, const QObject *data);
     union {
         void (*info)(Monitor *mon);
         void (*cmd)(Monitor *mon, const QDict *qdict);