clang-modernize -use-nullptr

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

Source/Core/DiscIO/BannerLoader.cpp

@@ -27,7 +27,7 @@ IBannerLoader* CreateBannerLoader(DiscIO::IFileSystem& _rFileSystem, DiscIO::IVo
 		return new CBannerLoaderGC(_rFileSystem, pVolume);
 	}
 
-	return NULL;
+	return nullptr;
 }
 
 } // namespace