dawn@0: % cumnorm_inplace(x) - cumulative mean-normalization 
dawn@0: %
dawn@0: %  x: matrix to normalize
dawn@0: %
dawn@0: % Each column of x is normalized by dividing each sample by the mean of
dawn@0: % samples with indices smaller or equal to it.
dawn@0: %
dawn@0: % Mex function.
dawn@0: % Warning: the input argument is assigned to.  This is not matlab-kosher!