2006-06-27  Philip Lafleur  <plafleur@cvs.gnome.org>

  * gegl/gegl-eval-mgr.c,
  * gegl/gegl-have-visitor.c,
  * gegl/gegl-need-visitor.c,
  * gegl/gegl-node.[ch],
  * gegl/gegl-operation-composer.c,
  * gegl/gegl-operation-filter.c,
  * gegl/gegl-operation-source.c,
  * gegl/gegl-operation.[ch]: Changed API for need_rect calculation;
    A node's need_rect should be what is needed from it by its parents,
    not what it needs from its children. An operation sets the need_rects
    of its children using gegl_operation_set_need_rect(self) in its
    calc_need_rect() function.