Try to make simdag-test-dotload reproducible.
Comment extracted from this patch:
/* Hack: circumvent a bug in libcgraph, where the edges are not always given
* back in creation order. We sort them again, according to their sequence
* id. The problem appears to be solved (i.e.: I did not test it) in
* graphviz' mercurial repository by the following changeset:
* changeset: 8431:
d5f1fb7e8103
* user: Emden Gansner <erg@research.att.com>
* date: Tue Oct 11 12:38:58 2011 -0400
* summary: Make sure edges are stored in node creation order
* It should be fixed in graphviz 2.30 and above.
*/
