* movpos.c needs to be modified to cope with mixed MovPosChanges
  split MovPosChange into two structs, Change which is per-method
  and MovPosChange which has a set of Changes one per relevant method

  Methods have to call a new change_done which is a bit like
  motion_done but only does one Change and considers whether the
  whole MovPosComb is done.

  evaluate should have a cost or a time or something rather than
  just a count since wagglers are nearly free and points are not
  and we always want to change a waggler rather than a point

* There may be some fallout from the segment movfeat splitting
  eg in the gui or gui plan displayer.