Add gthread to glib check

Add gthread to glib check

	* configure.in: Add gthread to glib check

	* libsoup/soup-session.c: Make this an abstract class.

	* libsoup/soup-session-async.c: A SoupSession class for
	asynchronous gmain-based operation; replaces the old SoupSession.

	* libsoup/soup-session-sync.c: A SoupSession class for synchronous
	blocking operation for use with threaded apps.

	* libsoup/soup-types.h, libsoup/soup.h: add the new session
	subclasses

	* libsoup/soup-connection.c (soup_connection_connect_sync): Don't
	try to unref the socket if the socket creation fails.
	(soup_connection_reserve): New, to explicitly mark a connection as
	being in use without queueing a message on it.

	* libsoup/soup-dns.c (check_hostent): Oof. Fix the logic of the
	"block" flag to not be reversed.

	* libsoup/soup-message.c (finished): set status to FINISHED here.
	(soup_message_cancel): Gone; needs to be done at the session
	level.

	* libsoup/soup-message-queue.c: Add a mutex and make all of the
	operations thread-safe.

	* libsoup/soup-socket.c (disconnect_internal): Make this
	thread-safe.
	(soup_socket_connect): Make the sync case work correctly.

	* libsoup/Makefile.am: add the SoupSession subclasses

	* tests/Makefile.am: libsoup depends on libgthread now, so
	revserver doesn't need to explicitly.

	* tests/get.c, tests/auth-test.c, tests/simple-proxy.c: Use
	soup_session_async_new().