WIP: first solution for lost references issue

* The solution consists of attaching a bridge object
  to QObjects. If the host object is destroyed, the
  bridge object will notify the script client
* The bridge object attachment is optimized so it
  only happens if required (but still too often ...)
* The child object of QChildEvent gets a special
  handling since this object is almost dead in case
  of remove. This special handling consists of
  a special, stripped class which is used to
  only represent QObject in that particular case.

testdata/ruby/qtbinding.rb

@@ -545,6 +545,7 @@ class QtBinding_TestClass < TestBase
     # Ability to monitor native child objects
 
     parent = RBA::QScrollArea::new
+    parent.show  # this makes resize actually change the widget's size
     child = parent.viewport
 
     # ensure parent and child are working