Buffer::Unmap no longer return boolean

Made no sense: What do you want to do when your buffer doesn't unmap ?
Tt now throw a warning by itself in case of failure


Former-commit-id: f776af16787316bbe1d55686a1db2c2e0f79d210

include/Nazara/Utility/Buffer.hpp

@@ -50,7 +50,7 @@ class NAZARA_API NzBuffer : public NzResource, NzNonCopyable
 
 		bool SetStorage(nzBufferStorage storage);
 
-		bool Unmap() const;
+		void Unmap() const;
 
 		static bool IsSupported(nzBufferStorage storage);
 		static void SetBufferFunction(nzBufferStorage storage, BufferFunction func);