Start using `g_autoptr` and `g_autofree` in all GLib based code ? (libuca, etc)

[gabs1234]

These are some Glib macros that tell the compiler to automatically free any Heap variable before a return statement.
With this, you no longer need to call g_free() or g_object_unref().

Only caveat : You need to use GCC or CLANG (and also all your variables have to initialized before hand, but this is only natural). Maybe a deal breaker ?

Really not urgent, could simply make the codebase more modern, memory safe and readable.