obsmarker: rename precnode into prednode
Rename prednode (predecessors node) into precnode (precursors node) in markers
class. Use util.nouideprecwarn because markers doesn't have easy access to an
ui object.
The renaming is done according to
https://www.mercurial-scm.org/wiki/CEDVocabulary.
Differential Revision: https://phab.mercurial-scm.org/D243
# name space package to host third party extensions
from __future__ import absolute_import
import pkgutil
__path__ = pkgutil.extend_path(__path__, __name__)