trivial changes
Changes Graphviz dependency from gvc/graph to cgraph, although now realised that graphviz is not actually _used_ anywhere.
Correct use of node/edge/graph macros from graphviz/types.h
At least it doesn't crash now...
Random position setting on nodes
Mostly more debugging.
A successful attempt to get the nodes located based on their id, but still not based on the right algorithm
So we DO need libgvc for the layout, but we ALSO need graphviz >2.26 for this to work.
Adds optional libgraph compilation, with default libcgraph compilation.
nodesep 2.0 ok in both graph/cgraph cases
Merge branch 'graphviz_update'