Correct how filterIntersections work, seems c++ don't like how thing were done.

source/shapes/csg.cpp

@@ -101,13 +101,11 @@ bool CSG::intersectionAllowed(bool leftHit, bool inLeft, bool inRight)
     return false;
 }
 
-Intersect CSG::filterIntersections(Intersect &xs)
+void CSG::filterIntersections(Intersect &xs, Intersect &ret)
 {
     bool inl = false;
     bool inr = false;
 
-    Intersect ret = Intersect();
-
     int i;
 
     for(i = 0; i < xs.count(); i++)
@@ -128,8 +126,6 @@ Intersect CSG::filterIntersections(Intersect &xs)
             inr = !inr;
         }
     }
-
-    return ret;
 }
 
 void CSG::dumpMe(FILE *fp)