gnome-keyring New GcrSecretExchange functionality

[Stef Walter <stefw collabora co uk>]

I've created some API in gcr which allows use of our method for
exchanging secrets between processes. This is the DH key agreement
process we use in the Secret Service API [1] and for communicating with
our prompting subprocess.

The reason we need this as an API, is so that we can securely have the
gnome-shell handle the prompts for gnome-keyring [2].

Documentation of the API is here:

http://people.collabora.com/~stefw/gcr-docs/gcr-GcrSecretExchange.html

And the bug for implementation is here:

https://bugzilla.gnome.org/show_bug.cgi?id=656955

Anyone want to look this over before I merge it?

Cheers,

Stef


[1] http://standards.freedesktop.org/secret-service/ch07.html
[2] https://bugzilla.gnome.org/show_bug.cgi?id=652459