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/Core/Updatable.hpp

@@ -9,9 +9,12 @@
 
 #include <Nazara/Prerequesites.hpp>
 
-class NzUpdatable
+class NAZARA_API NzUpdatable
 {
 	public:
+		NzUpdatable() = default;
+		virtual ~NzUpdatable();
+
 		virtual void Update() = 0;
 };