Replaced CONFESS with throw std::exception in libslic3r, so now

libslic3r should be compilable without Perl.

xs/src/libslic3r/Fill/FillBase.cpp

@@ -34,7 +34,7 @@ Fill* Fill::new_from_type(const InfillPattern type)
     case ipArchimedeanChords:   return new FillArchimedeanChords();
     case ipHilbertCurve:        return new FillHilbertCurve();
     case ipOctagramSpiral:      return new FillOctagramSpiral();
-    default: CONFESS("unknown type"); return nullptr;
+    default: throw std::invalid_argument("unknown type");;
     }
 }