Merge remote-tracking branch 'remotes/qmp-unstable/queue/qmp' into staging

* remotes/qmp-unstable/queue/qmp:
  monitor: Add object_add class argument completion.
  monitor: Add object_del id argument completion.
  monitor: Add device_add device argument completion.
  monitor: Add device_del id argument completion.
  qmp: expose list of supported character device backends
  Use error_is_set() only when necessary
  QMP: allow JSON dict arguments in qmp-shell
  hmp: migrate command (without -d) now blocks correctly

Conflicts:
	blockdev.c

[PMM: resolved trivial conflict in blockdev.c]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

scripts/qmp/qmp-shell

@@ -31,6 +31,7 @@
 # (QEMU)
 
 import qmp
+import json
 import readline
 import sys
 import pprint
@@ -107,6 +108,8 @@ class QMPShell(qmp.QEMUMonitorProtocol):
                     value = True
                 elif opt[1] == 'false':
                     value = False
+                elif opt[1].startswith('{'):
+                    value = json.loads(opt[1])
                 else:
                     value = opt[1]
             qmpcmd['arguments'][opt[0]] = value