changegroup: replace changegroup with makechangegroup
As part of reducing the number of changegroup creation APIs, let's replace the
changegroup function with makechangegroup. This pushes the responsibility of
creating the outgoing set to the caller, but that seems like a simple and
reasonable concept for the caller to be aware of.
Differential Revision: https://phab.mercurial-scm.org/D668
#require docutils gettext
$ $TESTDIR/check-gendoc ru
checking for parse errors