Clang AST Call parser adding duplicates

[tiferrei]

The clang call parser seems to add duplicate calls when they're detected.
As a quick fix a cleanup() method has been added, but it's extremely hacky, and adding duplicates would make the program extremely inefficient when ran over large codebases.

[tiferrei]

💡: One thing that might help using saving functions and calls directly as a Boost Graph. This will avoid duplicates and some unnecessary loops.