HostInterface: Add "Sync To Host Refresh Rate" option

src/core/settings.h

@@ -82,6 +82,7 @@ struct Settings
   float emulation_speed = 1.0f;
   float fast_forward_speed = 0.0f;
   float turbo_speed = 0.0f;
+  bool sync_to_host_refresh_rate = true;
   bool increase_timer_resolution = true;
   bool start_paused = false;
   bool start_fullscreen = false;