Build summary arcs

Created by: jacosro

Build summary arcs in the SDG. Two steps:

• Naive: Check reachability from formal_in to formal_out nodes
• Complete: Use the procedure described in SDG original paper (section 3.2) to build summary arcs in special cases such as recursion and reciprocal function calls

EDIT 07/06/20:

• Parameters with primitive type don't need to be processed. Summary arcs should be added from its actual_in to its corresponding actual_out without any need of processing
• output nodes act like formal_out/actual_out nodes, their summary arcs must be computed
• Global variables must be computed to, and they have to be treated as normal parameters in terms of computing summary arcs

Taking this into account, to solve this issue, the following issues must be completed first:

• #35 (closed)
• #34 (closed)

@cargaji