qjson: Handle "\f"

It's valid JSON and should be handled.
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>

json-parser.c

@@ -206,6 +206,10 @@ static QString *qstring_from_escaped_str(JSONParserContext *ctxt, QObject *token
                 qstring_append(str, "\b");
                 ptr++;
                 break;
+            case 'f':
+                qstring_append(str, "\f");
+                ptr++;
+                break;
             case 'n':
                 qstring_append(str, "\n");
                 ptr++;

qjson.c

@@ -158,6 +158,9 @@ static void to_json(const QObject *obj, QString *str)
                 case '\b':
                     qstring_append(str, "\\b");
                     break;
+                case '\f':
+                    qstring_append(str, "\\f");
+                    break;
                 case '\n':
                     qstring_append(str, "\\n");
                     break;