moments.c

[Jason Stover]

I'm using moments.c in regression.q and I think there is problem: It
requires two data passes. If we want PSPP to handle large data sets
well, it needs to be able to compute moments in a single data pass.
Does anyone mind if I modify moments.c to do so?

Second question: moments.c could also be made to compute correlations
between variables in a single data pass. If changing it to do so
doesn't make a mess of moments.c, does anyone mind if I make that
modification, too?

-Jason