Comment 1 for bug 1060236

I did a pull request about this ticket: https://github.com/buildout/buildout/pull/22

It makes the 3 examples provided in the ticket description above pass.
On the other side, it changes the behaviour of the multiple inheritance.

The motivation for the behaviour change is:

* develop bases as independant components
* inherit all properties of bases
* override some properties if necessary

Another note.... in http://pypi.python.org/pypi/zc.buildout/1.6.3#multiple-configuration-files:

``extends = b1.cfg b2.cfg b3.cfg`` gives ``${debug:op2} == b2 2``
but ``extends = b2.cfg b1.cfg b3.cfg`` (order changed) gives ``${debug:op2} == b1 2``

With the pull request, we'd get respectively "b1 2\nb2 2" and "b2 2\nb1 2".