fixed spatstat links (spatstat dropped gpc.poly support in version 1.34-0)
- changed version number: 0.3-2 -> 0.4-0
- package rgeos is no longer strictly required (moved to Suggests)
- coerce-methods between "Polygons" and "gpc.poly" have been dropped
- new functions gpc2owin and owin2gpc (similar to those dropped from
  package spatstat since version 1.34-0)
- Bugfix: "SpatialPolygons" of length > 1 did not work in polyCub.SV & Co.