ABUT:  put noncontiguous FMRI slices together [for to3d]

method: put zero valued slices in the gaps, then
        replicate images to simulate thinner slices

   abut [-dzin thickness] [-dzout thickness] [-root name]
        [-linear | -blocky] [-verbose] [-skip n+gap] ... images ...

   -dzin   the thickness value in mm;  if not given,
             taken to be 1.0 (in which case, the output
             thickness and gap sizes are simply relative
             to the slice thickness, rather than absolute)

   -dzout  the output slice thickness, usually smaller than
             the input thickness;  if not given, the program
             will compute a value (the smaller the ratio
             dzout/dzin is, the more slices will be output)

   -root   'name' is the root (or prefix) for the output
             slice filename;  for example, '-root fred.'
             will result in files fred.0001, fred.0002, ...

   -linear if present, this flag indicates that subdivided slices
             will be linearly interpolated rather than simply
             replicated -- this will make the results smoother
             in the through-slice direction (if dzout < dzin)

   -blocky similar to -linear, but uses AFNI's 'blocky' interpolation
             when possible to put out intermediate slices.
             Both interpolation options only apply when dzout < dzin
             and when an output slice has a non-gappy neighbor.

   -skip   'n+gap' indicates that a gap is to be inserted
             between input slices #n and #n+1, where n=1,2,...;
             for example, -skip 6+5.5 means put a gap of 5.5 mm
             between slices 6 and 7.

   More than one -skip option is allowed.  They must all occur