New file containing SoupMessagePrivate and some other

New file containing SoupMessagePrivate and some other

	* libsoup/soup-message-private.h: New file containing
	SoupMessagePrivate and some other soup-message-internal
	types/functions. Also includes the new, expanded SoupMessageStatus
	enum.

	* libsoup/soup-message-io.c: Replaces what used to be in
	soup-transfer, but now all the interfaces take SoupMessages
	instead of SoupReader/SoupWriter and deal with maintaining
	msg->priv->{read,write}_state themselves. Fixes up all the
	refcounting madness.

	* libsoup/soup-message-handlers.c: Move the handler code here,
	mostly unchanged. (But rename SoupHandlerType to SoupHandlerPhase
	to make the distinction from SoupHandlerKind clearer.)

	* libsoup/soup-message.c: Update for soup-message-io and new
	SoupMessageStatus values. Remove handler code.
	(soup_message_cleanup): Remove the hack to try to preserve the
	connection if the message gets cleaned up before it finishes
	reading. soup_message_requeue handles this in the requeuing case,
	and there's no especially compelling reason to bother doing it in
	any other case. (And the soup-message-io api doesn't support
	having a read operation that's not connected to any message.)

	* libsoup/soup-private.h: remove SoupMessagePrivate

	* libsoup/soup-queue.c: Update for soup-message-io and new
	SoupMessageStatus values.

	* libsoup/soup-server-message.c: Likewise

	* libsoup/soup-server.c: Likewise

	* libsoup/soup-transfer.c: Gone (yay)

	* libsoup/Makefile.am (libsoup_2_2_la_SOURCES): update