Consistency update

Unattractive update:
- Audio: GetListenerDirection was using ALfloat and GetListenerRotation not.
- ByteArray: Two return *this, hazh is perturbing, is it intended ?
- String: Same ?
- Camera: Adds of security (don't think it's usefull)
- Parser: size() = 0 -> empty()
- Utility: update 13 to 14 was forgotten in the previous patch just made
- VertexDeclaration: same
You are perfectly right, I don't know why I didn't used empty() in the first place.