Added preliminary version of transitive_reduction. This has no test or

documentation, and needs to be thoroughly reviewed.


[SVN r52562]

libs/graph

@@ -1 +1 @@
-Subproject commit 16e79e3bc5e5b1ee6719da040844c7ed431ba9dc
+Subproject commit 534e7f6acdeaba755345163615409aaaa5d04cfa