performance tuning

[Katsuhiro Kondou]

Innd consumes CPU time in processing ARTclean(), which
Barry already noted before.  I probably find where it
is.  Data copying(*out++ = *in++;).  This is done for
all incoming articles.  And I found there are two other
places to data copy.  One is end part of NCproc(), and
the other is ARTstore().

I think I can fix this, but I'd change SMstore() interface
to use writev() style, and some of processing in ARTclean()
need to be done in NCproc().

Any comments?
-- 
Katsuhiro Kondou