smurf: with ast.skip, make sure at least one real iteration is done

Previously, if ast.skip was set, it was possible for convergence to be
flagged at the end of the initial preparatory iterations, without any
real iterations being done.
smurf: New script to give approx map region from a raw file

The "rawregion" script returns an AST circle in a text file, calculated
from the MAP_HGHT, MAP_WDTH, BASEC1, BASEC2 and TRACKSYS FITS headers in
the supplied file.