Decouple save states from UI.

It's the UI's job to decide how and what things are displayed, not Core's.
This also reduces reasons for linkage issues.

UI/NativeApp.cpp

@@ -489,8 +489,13 @@ void NativeInit(int argc, const char *argv[], const char *savegame_dir, const ch
 	}
 #endif
 
-	if (!boot_filename.empty() && stateToLoad != NULL)
-		SaveState::Load(stateToLoad);
+	if (!boot_filename.empty() && stateToLoad != NULL) {
+		SaveState::Load(stateToLoad, [](bool status, const std::string &message, void *) {
+			if (!message.empty()) {
+				osm.Show(message, 2.0);
+			}
+		});
+	}
 
 	screenManager = new ScreenManager();
 	if (skipLogo) {