HostDisplay: Add an option to decouple display fps from emulator fps

Makes Android so much faster...

src/core/host_interface.cpp

@@ -463,6 +463,7 @@ void HostInterface::SetDefaultSettings(SettingsInterface& si)
   si.SetBoolValue("Display", "Fullscreen", false);
   si.SetBoolValue("Display", "VSync", true);
   si.SetStringValue("Display", "PostProcessChain", "");
+  si.SetFloatValue("Display", "MaxFPS", 0.0f);
 
   si.SetBoolValue("CDROM", "ReadThread", true);
   si.SetBoolValue("CDROM", "RegionCheck", true);