accidental ABI break

[Dan Winship <danw gnome org>]

libsoup 2.54.0 accidentally broke ABI (by adding a member to
SoupAuthClass and not removing a padding member to compensate).
(https://bugzilla.gnome.org/show_bug.cgi?id=765222,
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=821274) Is there a
preferred way for dealing with this? I'd like to just belatedly remove
the padding member to get back to the old ABI and then declare 2.54.0 to
have never happened, but that is slightly problematic in that most
distros probably currently have packages that were built against the
2.54.0 sources, so they would need to make sure to rebuild everything
that depends on libsoup after packaging 2.54.1. But if they're going to
have to do that, then maybe I should just embrace the ABI break and bump
the .so version and force the rebuild anyway? Or maybe I can get away
with just undoing the break and sending a warning to distributors@ ?

-- Dan