Improve Integer Scaling behavior

...so it always upscales the display from the framebuffer to fit the aspect ratio by stretching either horizontally or vertically instead of always stretching horizontally, which sometimes (actually most of the time) downscales the image

src/core/settings.h

@@ -143,6 +143,7 @@ struct Settings
   bool display_show_enhancements = false;
   bool display_all_frames = false;
   bool display_internal_resolution_screenshots = false;
+  bool display_always_stretch_horizontally = false;
   bool video_sync_enabled = DEFAULT_VSYNC_VALUE;
   float display_osd_scale = 100.0f;
   float display_max_fps = DEFAULT_DISPLAY_MAX_FPS;