#755 re-classify re-sorts messages

[Ivan]

just upgraded from 20.1 and the second thing i noticed
(after the history columns being too narrow) was that
reclassifying the messages RE-SORTS them; in other
words i have 700 messages and three buckets: HOT, KEEP,
SPAM. I sort the messages by bucket, and HOT appears at
the top. A message that erroneously was classified HOT
by popfile is really spam. i manually reclassify it to
be SPAM and press reclassify. The message is
reclassified as SPAM, but it appears that all the
messages are again sorted by bucket (not just ordered
on the page, the entire 700 messages seem to be
reprocessed). This time, the SPAM message is sorted
into the SPAM bucket, and no longer appears on the
page. I now have to again reclassify the messages on
the page, until no messages require re-classification,
at which point i can remove the page.

Reclassify should only mark the message with the
correct bucket, and then leave the displayed messages
on the page (i.e. don't resort the entire mailbox again).