stablerange: introduce a basic-mergepoint method This method use the new 'mergepoint' based stable sorting. It is expected to be eventually better than branch point to stable range: more stable, easier to cache, etc. Having a basic implementation will allow use to validate more advanced implementation.

# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)