Fix the issue with dag_shortest_paths discussed in

http://article.gmane.org/gmane.comp.lib.boost.devel/111573/


[SVN r27596]

libs/graph

@@ -1 +1 @@
-Subproject commit 76483e6dcccb07063ab2a75fd14e1f910618e419
+Subproject commit 3c045dd60e079f9202239afb576cbbe689464470