revset: added filter method to _addset
This method is intended to duck-type baseset, so we will still have _addset
as a private class but we will be able return it without wrapping it into an
orderedlazyset or a lazyset.
.. Common link and substitution definitions.
.. |hg(1)| replace:: **hg**\ (1)
.. _hg(1): hg.1.html
.. |hgrc(5)| replace:: **hgrc**\ (5)
.. _hgrc(5): hgrc.5.html
.. |hgignore(5)| replace:: **hgignore**\ (5)
.. _hgignore(5): hgignore.5.html