CHANGES IN 'ltsa' VERSION 1.46 (2015-08-21)
    o    improved documentation exactLoglikelihood()
    o    innovationVariance()
CHANGES IN 'ltsa' VERSION 1.45 (2015-08-21)
    o    new function exactLoglikelihood()
    o    fixed warnings by adjusting namespace,
    importFrom("stats", "ARMAtoMA", "convolve", "fft", "rnorm", "toeplitz")
CHANGES IN 'ltsa' VERSION 1.42,1.43,1.44 (2012-12-14)
    o    minor documentation fixes
CHANGES IN 'ltsa' VERSION 1.41 (2011-05-16)
    o    minor issue with DHSimulate fixed
CHANGES IN 'ltsa' VERSION 1.4 (2010-11-30)
    o    fixed NAMESPACE problem