Fix bugs 430, 426, 429, 394, 433.

These bugs are about QApplication instance being destroyed  before
some QObject.

Reviewer: Luciano Wolf <luciano.wolf@openbossa.org>
          Renato Araújo <renato.filho@openbossa.org>

tests/QtGui/bug_429.py

@@ -0,0 +1,10 @@
+from PySide.QtCore import *
+from PySide.QtGui import *
+import sys
+
+app = QApplication(sys.argv)
+scene = QGraphicsScene()
+label = QLabel("hello world")
+label.show()
+QTimer.singleShot(0, label.close)
+exit(app.exec_())