clang-modernize -use-nullptr

and s/\bNULL\b/nullptr/g for *.cpp/h/mm files not compiled on my machine

Source/Core/VideoBackends/D3D/NativeVertexFormat.cpp

@@ -20,7 +20,7 @@ class D3DVertexFormat : public NativeVertexFormat
 	ID3D11InputLayout* m_layout;
 
 public:
-	D3DVertexFormat() : m_num_elems(0), m_vs_bytecode(NULL), m_layout(NULL) {}
+	D3DVertexFormat() : m_num_elems(0), m_vs_bytecode(nullptr), m_layout(nullptr) {}
 	~D3DVertexFormat() { SAFE_RELEASE(m_vs_bytecode); SAFE_RELEASE(m_layout); }
 
 	void Initialize(const PortableVertexDeclaration &_vtx_decl);