This involved a few fixes.  To start with,
an virDomainSnapshot object is really tied to a
domain, not a connection, so we have to generate
a slightly different object so that we can get
at self._dom for the object.

Next, we had to "dummy" up an override piece of
XML with a bogus argument that the function doesn't
actually take.  That's so that the generator places
virDomainRevertToSnapshot underneath the correct
class (namely, the virDomain class).

Finally, we had to hand-implement the
virDomainRevertToSnapshot implementation, ignoring the
bogus pointer we are being passed.

With all of this in place, I was able to successfully
take a snapshot and revert to it using only the
Python bindings.

Signed-off-by: Chris Lalancette <clalance@redhat.com>

* python/libvirt-override.c (initlibvirtmod): Upon virInitialize
failure, skip the Py_InitModule call.

This introduces a new event type

   VIR_DOMAIN_EVENT_ID_IO_ERROR_REASON

This event is the same as the previous VIR_DOMAIN_ID_IO_ERROR
event, but also includes a string describing the cause of
the event.

Thus there is a new callback definition for this event type

typedef void (*virConnectDomainEventIOErrorReasonCallback)(virConnectPtr conn,
                                                           virDomainPtr dom,
                                                           const char *srcPath,
                                                           const char *devAlias,
                                                           int action,
                                                           const char *reason,
                                                           void *opaque);

This is currently wired up to the QEMU block IO error events

* daemon/remote.c: Dispatch IO error events to client
* examples/domain-events/events-c/event-test.c: Watch for
  IO error events
* include/libvirt/libvirt.h.in: Define new IO error event ID
  and callback signature
* src/conf/domain_event.c, src/conf/domain_event.h,
  src/libvirt_private.syms: Extend API to handle IO error events
* src/qemu/qemu_driver.c: Connect to the QEMU monitor event
  for block IO errors and emit a libvirt IO error event
* src/remote/remote_driver.c: Receive and dispatch IO error
  events to application
* src/remote/remote_protocol.x: Wire protocol definition for
  IO error events
* src/qemu/qemu_monitor.c, src/qemu/qemu_monitor.h,
  src/qemu/qemu_monitor_json.c: Watch for BLOCK_IO_ERROR event
  from QEMU monitor

This binds the virDomainGetBlockInfo API to python's blockInfo
method on the domain object

>>> c = libvirt.openReadOnly('qemu:///session')
>>> d = c.lookupByName('demo')
>>> f = d.blockInfo("/dev/loop0", 0)
>>> print f
[1048576000L, 104857600L, 104857600L]

* python/libvirt-override-api.xml: Define override signature
* python/generator.py: Skip C impl generator for virDomainGetBlockInfo
* python/libvirt-override.c: Manual impl of virDomainGetBlockInfo

I have primarily followed the pattern of the 'secret' driver to provide
support for the missing python bindings for the network filter API.

The generator code was totally wrong for the virDomainSnapshot
APIs, not generating the wrapper class, and giving methods the
wrong names

* generator.py: Set metadata for virDomainSnapshot type & APIs
* libvirt-override-api.xml, libvirt-override.c: Hand-code the
  virDomainSnapshotListNames glue layer

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

Introduce a new public API that provides a way to get progress
info on currently running jobs on a virDomainpPtr. APIs that
are initially within scope of this idea are

 virDomainMigrate
 virDomainMigrateToURI
 virDomainSave
 virDomainRestore
 virDomainCoreDump

These all take a potentially long time and benefit from monitoring.
The virDomainJobInfo struct allows for various pieces of information
to be reported

 - Percentage completion
 - Time
 - Overall data
 - Guest memory data
 - Guest disk/file data

* include/libvirt/libvirt.h.in: Add virDomainGetJobInfo
* python/generator.py, python/libvirt-override-api.xml,
  python/libvirt-override.c: Override for virDomainGetJobInfo API
* python/typewrappers.c, python/typewrappers.h: Introduce wrapper
  for unsigned long long type

* python/libvirt-override.c (libvirt_virConnectBaselineCPU): Don't leak
the xmlcpus buffer upon encountering a non-string list element.