(Relay) Handle unexpected replies and disconnections adequately

- Previously it was possible that MgSMTP erroneously administered
an e-mail as delivered, when the server accepted the recipient in
the RCPT stage, but disconnected before or in the DATA stage.
This patch mainly addresses this issue, by making sure that the
transaction is completed, before administering a final status.

- MgSMTP is now more tolerant with non-compliant replies,
e.g., accepts 250 for connection opening, not only 220.

- Increased relay send buffer size from 32 lines to 64.

	modified:   Common.pas
	modified:   MgSMTP.pas
	modified:   Relay.pas
	modified:   Spool.pas