Ported intersect_expolygons() and subtract_expolygons() to XS

xs/xsp/typemap.xspt

@@ -7,6 +7,7 @@
 %typemap{AV*};
 %typemap{Point*};
 %typemap{ExPolygon*};
+%typemap{ExPolygonCollection*};
 %typemap{Line*};
 %typemap{Polyline*};
 %typemap{Polygon*};