Prevent undefined behavior with integer under/overflow with help.Int()

It's possible that SDL_atoi() could call the libc atoi(), and if a
string is provided that's too large to fit into an integer, then that
would result in undefined behavior. To avoid this, use SDL_strtol()
instead.

desktop_version/src/UtilityClass.cpp

@@ -106,7 +106,7 @@ int UtilityClass::Int(const char* str, int fallback /*= 0*/)
 		return fallback;
 	}
 
-	return SDL_atoi(str);
+	return (int) SDL_strtol(str, NULL, 0);
 }
 
 std::string UtilityClass::GCString(std::vector<SDL_GameControllerButton> buttons)