Activate workaround only for boost < 1.79

Installation/include/CGAL/config.h

@@ -598,6 +598,8 @@ inline std::string data_file_path(const std::string& filename)
 } // end namespace CGAL
 
 
+#if BOOST_VERSION < 107900
+
 // Workaround for an accidental enable if of Eigen::Matrix in the
 // boost::multiprecision::cpp_int constructor for some versions of
 // boost
@@ -650,4 +652,6 @@ namespace boost {
     }
 }
 
+#endif
+
 #endif // CGAL_CONFIG_H