(spam-split): do not require spam-use-CHECK to be

(spam-split): do not require spam-use-CHECK to be
enabled if that check is passed to spam-split explicitly; also
fix so 'spam doesn't get converted to spam-split-group when
spam-split-symbolic-return is t
(spam-find-spam): find registrations of the article and use those
instead of re-running spam-split to find the spam/ham
classification of the article
(spam-log-processing-to-registry, spam-log-registered-p)
(spam-log-unregistration-needed-p, spam-log-undo-registration):
use gnus-error instead of gnus-message
(spam-log-registration-type): new function to determine the
classification of a message based on registry entries; will
return nil if both 'spam and 'ham are found
(spam-check-BBDB): expand all the BBDB macros here so we can have
a reasonably fast local cache without the loading errors