gnome-keyring should use DBus for discovery

[Nate Nielsen <nielsen-list memberwebs com>]

Currently gnome-keyring-daemon uses an environment variable to
communicate its socket path to libgnome-keyring.

However this breaks down when applications are started early in the
session. seahorse-agent is one such application. (Early in the session,
it needs to setup environment variables to hook into SSH and GPG agents).

I've put together a patch which uses DBus to discover
gnome-keyring-daemon and find the appropriate socket to communicate on:

http://bugzilla.gnome.org/show_bug.cgi?id=400956

Any objections to me adding this into gnome-keyring?

Cheers,
Nate Nielsen