[Mimedefang] sa-mimedefang.cf read by spamassassin

[Kenneth Porter]

Doh, sorry I didn't mention this. The reason this came up is that SA 3 
(invoked from procmail) was failing to rewrite my subject and I found that 
rewrite_subject is no longer a valid config term. It's now "rewrite_header 
subject STRING":

# old rewrite_subject directive obsolete, changes to rewrite_header
#rewrite_subject 1
#subject_tag (SPAM? _HITS_)
rewrite_header subject [SPAM? _HITS_]

(Also note that parentheses are no longer valid in the STRING argument. If 
found, they're converted to brackets.)

SA should just silently ignore the "rewrite_subject 0" in sa-mimedefang.cf, 
so this isn't fatal. It will show up if you lint the config, though.