Reduce the scaling factor for attstattarget to number-of-lexemes from 100

Reduce the scaling factor for attstattarget to number-of-lexemes from 100
to 10, to compensate for the recent change in default statistics target.
The original number was pulled out of the air anyway :-(, but it was picked
in the context of the old default, so holding the default size of the
MCELEM array constant seems the best thing.  Per discussion.