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>
diff --git a/qjson.h b/qjson.h
index 7fce742..7afec2e 100644
--- a/qjson.h
+++ b/qjson.h
@@ -14,12 +14,14 @@
 #ifndef QJSON_H
 #define QJSON_H
 
+#include <stdarg.h>
 #include "qobject.h"
 #include "qstring.h"
 
 QObject *qobject_from_json(const char *string);
 QObject *qobject_from_jsonf(const char *string, ...)
     __attribute__((__format__ (__printf__, 1, 2)));
+QObject *qobject_from_jsonv(const char *string, va_list *ap);
 
 QString *qobject_to_json(const QObject *obj);