Changed select() timeout in sockprintf() from 1 to 5 minutes.
sockmsgtxt() now returns 0 if any header fields weren't sent successfully.
POP3 server actually checks the number of lines sent successfully and only
marks the message as 'read' if all lines requested were sent.
Now stores original, unmodified RFC822: to, from, and reply-to header fields.
Bounce-messages are now flagged as from an AGENT_PROCESS and messages from
processes aren't bounced (preventing bounced message loops).
Reduced mail server cycle time from 5 to 2 seconds (frequency at which recycle
semaphores are checked).