README:
- compile with cpl make scddns
- run as scddns [<input file>]
- <input file> defaults to scddns0.dat if omitted
- the input file contains a number of parameters of the form name=value, optionally followed by a velocity field as binary data
- if no binary data are present, a random initial field is generated
- output velocity fields, sequentially numbered as scddns<num>.dat, are in the same format as the input file; any one of them can be used to restart the computation.