if a parent object came from C++, and this is destroyed on python side this
leave a reference on the python child object.


Example:
 o = ObjectType() # this create o with refcount = 1

 # getCppParent() return a c++ object unknown by shiboken
 o.getCppParent().setObjectName('parent') # this increment the o refcount to  2
 o.getCppParent().setObjectName('parent') # this increment the o refcount to  3
 o.getCppParent().setObjectName('parent') # this increment the o refcount to  4