Broken link in Digraphs/doc/io.xml

[pramothragavan]

The excerpt is:

    A detailed definition of the DIMACS format can be found at
    <URL>http://mat.gsia.cmu.edu/COLOR/general/ccformat.ps</URL>, in Section
    2.1. Note that optional descriptor lines, as described in Section 2.1, will
    be ignored.

[reiniscirpons]

The old DIMACS webpage http://archive.dimacs.rutgers.edu/Challenges/ has the tex (not the pdfs) of the Challenge 1 (http://archive.dimacs.rutgers.edu/pub/netflow/general-info/specs.tex) and Challenge 2 (http://archive.dimacs.rutgers.edu/pub/challenge/graph/doc/ccformat.tex) specifications, which contain a description of the file format. It seems there is no authoritative webpage for the format anymore, so perhaps we should just include the format description from the challenge specs in the doc explicitly (it is not too involved I think).

[wilfwilson]

I'll sort something out.

[james-d-mitchell]

Resolved by recent pr.