C++17ification.

C++17ification!

- Filesystem interaction now uses std::filesystem::path.
- Usage of const char*, std::string have been changed to
  std::string_view where appropriate.
- Usage of printf-style functions changed to use fmt.

src/xenia/gpu/null/null_graphics_system.h

@@ -2,7 +2,7 @@
  ******************************************************************************
  * Xenia : Xbox 360 Emulator Research Project                                 *
  ******************************************************************************
- * Copyright 2016 Ben Vanik. All rights reserved.                             *
+ * Copyright 2020 Ben Vanik. All rights reserved.                             *
  * Released under the BSD license - see LICENSE in the root for more details. *
  ******************************************************************************
  */
@@ -26,7 +26,7 @@ class NullGraphicsSystem : public GraphicsSystem {
 
   static bool IsAvailable() { return true; }
 
-  std::wstring name() const override { return L"null"; }
+  std::string name() const override { return "null"; }
 
   X_STATUS Setup(cpu::Processor* processor, kernel::KernelState* kernel_state,
                  ui::Window* target_window) override;