Define two new signals, request_queued and request_unqueued, to provided a

Define two new signals, request_queued and request_unqueued, to provided a

        * libsoup/soup-session.c: Define two new signals, request_queued
        and request_unqueued, to provided a clearer (and
        clearly-documented) lifecycle for messages, helping us (and other
        people) avoid bugs like #522601, SoupSession::authenticate signal
        emitted multiple times per message (reported and analyzed by Tommi
        Komulainen).

        * libsoup/soup-logger.c:
        * libsoup/soup-auth-manager.c:
        * libsoup/soup-auth-manager-ntlm.c: Use request_queued/unqueued

        * tests/auth-test.c (do_async_auth_test): add a regression test

svn path=/trunk/; revision=1110