determines bvar function scaling factor
[scale]=scstd(y,nobs,nlag)
* y = an (nobs x neqs) matrix of y-vectors in levels
* nobs = # of observations in y
* nlag = the lag length
* scale = std deviation of the residuals
scale(j,1) = scstd(ytmp,nobs,nlag); // Example taken from function bvar1 (!)