Mark up some more vc7 failures in the graph lib

[SVN r28417]

status/explicit-failures-markup.xml

@@ -552,6 +552,8 @@
             <test name="bundled_properties"/>
             <test name="dfs_cc"/>
             <test name="dijkstra_cc"/>
+            <test name="floyd_warshall_test"/>
+            <test name="graphviz_test"/>
             <test name="subgraph"/>
             <test name="transitive_closure_test"/>
             <test name="vector_graph_cc"/>