This commit introduce separate types (e.g. GDNativeStringPtr vs GDNativeUninitializedStringPtr)
depending on if the pointed data is already initialized (C++ style where constructor is alway
called when create a variable even if it is to be passed as return value) or not (C style).
On top of that, small changes has been made to `GDNativeInterface` so that it methods are
consistent on using uninitialized return value.
e785dd9dd9