CPU: Implement PGXP CPU Mode

This is *very* slow. You don't want to enable it if you don't need it.
It is also incompatible with the recompiler and will disable it if the
option is enabled.

src/core/host_interface.h

@@ -134,6 +134,9 @@ protected:
   /// Saves current settings variables to ini.
   virtual void SaveSettings(SettingsInterface& si);
 
+  /// Checks and fixes up any incompatible settings.
+  virtual void FixIncompatibleSettings();
+
   /// Checks for settings changes, std::move() the old settings away for comparing beforehand.
   virtual void CheckForSettingsChanges(const Settings& old_settings);