libdbus Missing Async Calls

[Lawrence D'Oliveiro]

In Dbussy <https://github.com/ldo/dbussy>, I have been able to provide
async variants of every part of the connection setup process, except
the initial dbus_connection_open/dbus_connection_open_private calls:
these calls are synchronous only.

Alternatively, it would be handy if I could pass in an
already-connected socket FD, for libdbus to wrap in a connection object.