Numerous changes:

- Fixed line counter/return value of sockmimetext() - did not count last line
if not \n terminated.
- If a POP3 "TOP" command is used to request more lines than there are bytes
in message body, just send all lines and don't log an error.
- JS mailproc error reporting and log() method now includes the mail-proc
name and the "SMTP" log prefix. "JavaScript:" is no longer included as part
of the log() output since that is implied by the mailproc name.
- js_mailproc() now reuses the same runtime, context, and global object to
speed up the initialization/execution of multiple JS mailprocs per message.
- Beginning support for messages to be bounced back to mailprocs (e.g.
ListServer), specifically by ignoring bounces of SMTP sys messages
(instead of all non-person agent types). More work in bounce() is needed.