Hopefully a fix of https://github.com/prusa3d/Slic3r/issues/11

Replaced eval { die } construct with a bool return value indicating
success or failure of an automatic arrangement of parts on the print bed.

Don't know exactly what is happening here, but throwing a "die" inside
a XS function and then catching it inside an eval {} block is suspcious.

xs/src/libslic3r/Geometry.hpp

@@ -26,7 +26,11 @@ double deg2rad(double angle);
 void simplify_polygons(const Polygons &polygons, double tolerance, Polygons* retval);
 
 double linint(double value, double oldmin, double oldmax, double newmin, double newmax);
-Pointfs arrange(size_t num_parts, const Pointf &part_size, coordf_t gap, const BoundingBoxf* bed_bounding_box);
+bool arrange(
+    // input
+    size_t num_parts, const Pointf &part_size, coordf_t gap, const BoundingBoxf* bed_bounding_box, 
+    // output
+    Pointfs &positions);
 
 class MedialAxis {
     public: