add SOUP_SSL_ERROR_CERTIFICATE.

add SOUP_SSL_ERROR_CERTIFICATE.

	* libsoup/soup-ssl.h (SoupSocketError): add
	SOUP_SSL_ERROR_CERTIFICATE.

	* libsoup/soup-gnutls.c (do_handshake): Pass the GError to
	verify_certificate.
	(verify_certificate): Set the GError appropriately rather than
	spewing g_warnings.

	* libsoup/soup-socket.c (read_from_network, soup_socket_write): If
	the GIOChannel operation returns an error, store it as GOBject
	data on the socket (as a hack so soup-message-io.c can access it
	without us needing to change SoupSocket's API).

	* libsoup/soup-message-io.c (io_error): peek at the socket's
	"last_error" datum and set the message's status to SSL_FAILED
	(with the GError's message string) rather than IO_ERROR, if
	appropriate. For 64414.