Be more aggressive about closing unused persistent connections

	Be more aggressive about closing unused persistent connections
	when needed, to avoid slow load times in WebKit.

	* libsoup/soup-session-async.c (run_queue): Remove the
	"try_pruning" flag from here and from all the callers, and
	*always* try pruning idle connections if it would help.

	* libsoup/soup-session.c (soup_session_try_prune_connection):
	Rather than only closing a single connection, close all idle
	connections.

svn path=/trunk/; revision=1119