Changes:
* fix a problem with handling of exceptions that was uncovered by
Python 2.3.
* disable assigning to unknown attributes on stub instances. Saves
a little memory too.
* add CORBA.ORB.work_pending() and CORBA.ORB.perform_work() methods.
Changes (since 1.99.5):
* Work with latest HEAD branch (ORBit2 2.7.x).
* allow importing of CORBA or PortableServer without first importing
ORBit. This gives better compatibility with standard CORBA mapping.
* None is not a valid string/wstring value.
* accept strings for sequence<octet>.
* clean up base class list when building client stubs. This is
needed in order for the stubs to work with Python 2.3.
* fix some possible segfaults if the argument names are missing in
the IInterface structures, which occurs when using ORBit.load_file().
