The generator was disabled for the new event callbacks, since they
need to be hand written. This patch adds the C and python glue to
expose the new APIs in the python binding. The python example
program is extended to demonstrate of the code
* python/libvirt-override.c: Registration and dispatch of events
at the C layer
* python/libvirt-override-virConnect.py: Python glue for events
* examples/domain-events/events-python/event-test.py: Demo use
of new event callbacks