Implement a basic borrow checker to avoir memory leaks on struct instantiation

[Champii]

We introduced heap allocated structs in #179 that uses the system provided malloc().
This introduces a memory leak for each struct instance, and must obviously be mitigated by inserting corresponding free() call when the struct is not used anymore.

This will be the first basic implementation that will not cover all use-cases nor be perfect, but will serve as a prototype that will shed light on the actual scope and features of this borrow checker.