o Compare with   library( fracdiff )  -- and 'ts2test' :
    --> partly happened in "Semesterarbeit" by Thomas Grischott
	(-> /u/maechler/save/papers/RGrischott-LongMem.pdf
	  and /sfs/a/A/SfS-students/groman/RAusw/ )
  --> Completely merge with the also unreleased package ../ts2test !!

o provide  logLik() methods .. For WhittleEst(), should be straightforward,
  using Jan's book and Qeta().

o Think about adding Graf's  *robust* estimators ("HUBINC" et al.).
  ---> package ../ts2test/ which has M() !

o specFGN(eta, m, nsum)  becomes quite slow for "large" m
  (e.g m = 2^16; the for loop takes time).
  Should do this in C code!
