qapi: rename QmpOutputVisitor to QObjectOutputVisitor

The QmpOutputVisitor has no direct dependency on QMP. It is
valid to use it anywhere that one wants a QObject. Rename it
to better reflect its functionality as a generic QAPI
to QObject converter.

The commit before previous renamed the files, this one renames C
identifiers.

Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1475246744-29302-6-git-send-email-berrange@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Split into file rename and identifier rename]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/scripts/qapi-event.py b/scripts/qapi-event.py
index 6d9a36d..f4eb7f8 100644
--- a/scripts/qapi-event.py
+++ b/scripts/qapi-event.py
@@ -98,7 +98,7 @@
 
     if arg_type and not arg_type.is_empty():
         ret += mcgen('''
-    v = qmp_output_visitor_new(&obj);
+    v = qobject_output_visitor_new(&obj);
 ''')
         if not arg_type.is_implicit():
             ret += mcgen('''