Xerces-C 3.1 transition

[Scott Cantor]

> This looks like fallout from the new library being built with 3.1, because
> the dev package was upgraded, but XML-Security-C being built with 3.0.  My
> guess is that rebuilding XML-Security-C with 3.1 will fix it, but we'll
> probably need to go through all the packages and do another transition.
> (There are new versions available for all of them anyway, though, so we'd
> be doing that regardless.)

I know it's "unstable", but FWIW 3.1 isn't actually released yet.

But in any case, yes, all the packages have to be built with the same
version, the namespace in Xerces changes with every minor release for some
reason.

-- Scott