Use dlopen(), dlsym() and dlclose() to launch functions.

[Dadoum]

It would be a big refactor, but will permit to not rely on the Swift's messy pkgBuild implementation

[rhx]

We would still need to generated code based on the .gir file if we want to use idiomatic Swift. This is different from weakly typed languages such as Python, that simply use object-introspection at run time. Also, the advantage of letting the compiler do the hard work is that we can achieve similar performance as the underlying C/C++ interface and capture most errors at compile time (rather than run time).