Suppression of warnings

OffsetOf: use of static_cast
Updatable: API and virtual destructor
Drawable: virtual destructor
Vector: std::abs should be "the" abs.
AbstractClass: API
+Updatable: Like for others abstracts
Buffer: nullptr for pointer to function.
Image: wasn't returning a vector.

Former-commit-id: 57e0009286a02b9e3b0b81945e500d7d9e466ae2

include/Nazara/Graphics/Drawable.hpp

@@ -13,7 +13,7 @@ class NAZARA_API NzDrawable
 {
 	public:
 		NzDrawable() = default;
-		~NzDrawable();
+		virtual ~NzDrawable();
 
 		virtual void Draw() const = 0;
 };