adds a new python API call for retrieving the running
hypervisor version used by a connection: virConnectGetVersion

* python/generator.py: skip virConnectGetVersion from autogenerated
* python/libvirt-override-api.xml python/libvirt-override.c: define
  direct native bindings

Enable virDomainMemoryStats in the python API.  dom.memoryStats() will return a
dictionary containing the supported statistics.  A dictionary is required
because the meaining of each quantity cannot be inferred from its index in a
list.

* python/generator.py: reenable bindings for this entry point
* python/libvirt-override-api.xml python/libvirt-override.c: the
  generator can't handle this new function, add the new binding,
  and the XML description

* libvirt-override.c: Add many missing calls to allow threading
  when entering C code, otherwise python blocks & then deadlocks
  when we have an async event to dispatch back into python code.
  Fix return value check for virDomainPinVcpu binding.

* python/generator.py python/libvirt-override-api.xml
  python/libvirt-override.c: implement the bindings for
  virConnectListInterfaces() and virConnectListDefinedInterfaces()

There is currently no way to determine the libvirt version of a remote
libvirtd we are connected to. This is a useful piece of data to enable
feature detection.

suggested by danpb on irc, patch by danken fixed for proper C syntax

* python/libvirt-override.c: on event callback release the python
  interpreter lock and take it again when coming back so that the
  callback can reinvoke libvirt.

* README: New file describing what each file is used for
* livvirt-override.c, libvirt-override.py, libvirt-override-api.xml,
  libvirt-override-virConnect.py: Manually written code overriding
  the generator
* typewrappers.c, typewrappers.h: Data type wrappers
* generator.py: Automatically pre-prend contents of libvirt-override.py
  to generated libvirt.py. Output into libvirt.py directly instead of
  libvirtclass.py. Don't generate libvirtclass.txt at all. Write C
  files into libvirt.c/.h directly
* Makefile.am: Remove rule for creating libvirt.py from libvirt-override.py
  and libvirtclass.py, since generator.py does it directly