get/set auth/proxy_auth info for a message.

get/set auth/proxy_auth info for a message.

	* libsoup/soup-message.c (soup_message_set_auth)
	(soup_message_get_auth, soup_message_set_proxy_auth)
	(soup_message_get_proxy_auth): get/set auth/proxy_auth info for a
	message.

	* libsoup/soup-session.c (add_auth): Use soup_message_set_auth and
	soup_message_set_proxy_auth.
	(update_auth_internal): Call soup_message_get_auth or
	soup_message_get_proxy_auth to determine the message's prior auth,
	rather than calling lookup_auth() again, since it isn't guaranteed
	to return the same thing now as it did when the message was
	originally sent. Fixes erroneous 401s when queuing multiple
	messages at once to an as-yet-unauthenticated-to server. #271540

	* libsoup/soup-session-async.c (queue_message): don't run the
	queue right away, do it at idle time. Otherwise in some cases
	(especially errors), the message callbacks could be invoked before
	queue_message returns.

	* tests/auth-test.c: add a regression test for #271540.

svn path=/trunk/; revision=922