fix bd_dijkstra crash on MacOSX.

This will fix #136 issue(bd_dijkstra crashed server on MacOSX).

The crash occurred the following "push_back" line.
<pre>
bool BiDirDijkstra::construct_graph(edge_t* edges, int edge_count, int maxNode)
{
    :
    m_vecNodeVector.push_back(nodeInfo);
</pre>

I changed "m_vecNodeVector" type from "std::vector<GraphNodeInfo>" to "std::vector<GraphNodeInfo*>",
then, the crash didn't occurred on MacOSX.
I confirmed that bd_dijkstra test passed on Ubuntu 12.04 x86,
but, I hope someone review my modification.