correct some SWIG switches

Device/Beam/Beam.h

@@ -16,10 +16,13 @@
 #define BORNAGAIN_DEVICE_BEAM_BEAM_H
 
 #include "Base/Vector/Direction.h"
-#include "Base/Vector/EigenCore.h"
 #include "Fit/Param/RealLimits.h"
 #include "Param/Node/INode.h"
 
+#ifndef SWIG
+#include "Base/Vector/EigenCore.h"
+#endif
+
 class IFootprintFactor;
 
 //! An incident neutron or x-ray beam.