Add the missing degree() in Boost 1.62

This is a workaround that fixes issue #39

include/boost-patched/graph/reverse_graph.hpp

@@ -0,0 +1,27 @@
+#ifndef REVERSE_GRAPH_PATCHED_H_
+#define REVERSE_GRAPH_PATCHED_H_
+
+#include <boost/version.hpp>
+
+#include <boost/graph/reverse_graph.hpp>
+
+#if (BOOST_VERSION == 106200)
+
+// Boost 1.62.0 does not implement degree() in reverse_graph which is required
+// by BidirectionalGraph, so add it.
+
+namespace boost {
+
+template <class BidirectionalGraph, class GRef>
+inline typename graph_traits<BidirectionalGraph>::degree_size_type
+degree(const typename graph_traits<BidirectionalGraph>::vertex_descriptor u,
+       const reverse_graph<BidirectionalGraph,GRef>& g)
+{
+    return degree(u, g.m_g);
+}
+
+} // namespace boost
+
+#endif // Boost 1.62.0
+
+#endif