fix unused parameter warning

Base/Axis/IAxis.cpp

@@ -36,7 +36,7 @@ IAxis* IAxis::createClippedAxis(double lower, double upper) const
     return newAxis;
 }
 
-void IAxis::clip(double lower, double upper)
+void IAxis::clip(double /*lower*/, double /*upper*/)
 {
     throw std::runtime_error("IAxis::clip() -> Error. Not implemented.");
 }