Fix issue with undefined BOOST_VERSION

if BOOST_VERSION < 106000 always succeeds because BOOST_VERSION is
undefined.  In order to avoid the code for new boost, we need
<boost/version.hpp>

xs/src/libslic3r/Point.hpp

@@ -114,6 +114,7 @@ class Pointf3 : public Pointf
 }
 
 // start Boost
+#include <boost/version.hpp>
 #include <boost/polygon/polygon.hpp>
 namespace boost { namespace polygon {
     template <>