Gtk.Adjustment.__init__ overrides ignore value argument in Python 3

I suspect this is due to dict iteration ordering and in Python 2 this just worked by accident.

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk
adj = Gtk.Adjustment(1.5, -24., 12., 0.5, 3, 0)
assert adj.get_value() == 1.5

This works with Python 2.7 and fails with Python 3.6.

The workaround is to use Gtk.Adjustment.new