index: account for CRLF conversion when storing bytes
NNTP and IMAP both require CRLF conversions on the wire.
They're also the only components which care about
$smsg->{bytes}, so store the CRLF-adjusted value in over.sqlite3
and Xapian DBs..
This will allow us to optimize RFC822.SIZE fetch item in IMAP
without triggering size mismatch errors in some clients' default
configurations (e.g. Mail::IMAPClient), but not most others.
It could also fix hypothetical problems with NNTP clients that
report discrepancies between overview and article data.