Revert "Add type checking to positional Gtk.Box and Gtk.Window ctor arguments"

While this enforces correctness, this can cause new crashes in software which
incorrectly uses the GObject constructor and needs fixing. E. g. Ubuntu's
current sofware-center (wrongly) does

  Gtk.Box(Gtk.Orientation.HORIZONTAL)

which now causes a crash with this new check.

This reverts commit 2cc4dfaf877f202977de4a7ede24aa3bad7d91c8.
Fix toggleref safety problems by always enabling the GIL

Call PyEval_InitThreads for the base gi module import. This forces the
Python internals create the GIL and always support threading with the
various thread state enter/exit funcs. This is needed since we cannot
predict which GI repositories might accept Python callbacks and run them in
non-Python threads or trigger toggle ref notifications in a thread other
than main.

https://bugzilla.gnome.org/show_bug.cgi?id=709223
release 3.10.2
configure.ac: post-release version bump to 3.10.3