sparsegraph - sparsegraph: Changing sparsegraph_neighbors() to do binary

Log Message:
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Changing sparsegraph_neighbors() to do binary search, rather than linear search,
to look up a node's index given its label.  This takes advantage of what was
previously just an artifact of sparsegraph_impl.cpp which ensures that nodes
are inserted in increasing label order.

Modified Files:
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    sparsegraph:
        sparsegraph.c (r1.1.1.1 -> r1.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/sparsegraph/sparsegraph/sparsegraph.c.diff?r1=1.1.1.1&r2=1.2)
        sparsegraph.h (r1.1.1.1 -> r1.2)
        (http://cvs.pgfoundry.org/cgi-bin/cvsweb.cgi/sparsegraph/sparsegraph/sparsegraph.h.diff?r1=1.1.1.1&r2=1.2)