QJSON: Introduce qobject_from_jsonv() It accepts a va_list and will be used by QError. Also simplifies the code a little, as the other qobject_from_() functions can use it. Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com> Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>