Changes the logical parser to take in consideration the filename to disambiguate free function names

Free function's qualified name are now persisted as "@". This is not an ideal solution, as there may be two files with same name with functions of same name defined in different places, but it is a good heuristic for most projects.

Future implementations may need to take in consideration the compilation and/or linkage context to resolve and disambiguate function calls in a more formal way.