Create a DOT output formatter for GraphViz

[andymeneely]

Check out the format from here:

http://www.graphviz.org

[nuthanmunaiah]

Currently testing code that generates a per-function sub-graph of the entire call graph. This sub-graph shows:

• Node that represents the function in focus.
• Node to the upper right of the function node gives the number of indirect entry points.
• Node to the lower left of the function node gives the number of indirect exit points.
• Nodes that represent functions that are entry points (in red).
• Nodes that represent functions that are exit points (in orange).
• Nodes that represent functions that are both entry and exit points (in yellow).

TODO : There is still a bug that causes the sub-graph to indicate that there are indirect entry/exit points but there are no edges coming into/going out of this indicator node.

Examples