gnome-keyring Split gcr library base bits out

[Stef Walter <stefw collabora co uk>]

I'd like to use some parts of the gcr library (such as the parser) in
non-GTK programs. As I mentioned on desktop-devel-list, I've now split
parts of the GCR library into a base library that sits underneath the
usual one.

This is a minor ABI break (on non-ELF platforms), but not such a big
deal given the small amount of applications that link to the GCR library.

This has been committed to git master. It's always complex to do this
sort of autotools-fu, so if you notice anything amiss, let me know.

Cheers,

Stef