Add a function to send DATAOUT PDUs.

Update the send pdu command to trap when we need to send data to the target
but we are not allowed to send using immediate data.
For this case, send the data as a separate DATAOUT pdu instead.

Twiddle the flags and other fields to now manage that we send the data
as two separate PDUs.

lib/pdu.c

@@ -74,6 +74,8 @@ iscsi_allocate_pdu(struct iscsi_context *iscsi, enum iscsi_opcode opcode,
 	return iscsi_allocate_pdu_with_itt_flags(iscsi, opcode, response_opcode, iscsi->itt++, 0);
 }	
 
+
+
 void
 iscsi_free_pdu(struct iscsi_context *iscsi, struct iscsi_pdu *pdu)
 {