On dedicated servers, save copy of last autosave on crash

This is to avoid all autosaves being overwritten when the server
is auto-restarted with a new map

src/fios.h

@@ -136,7 +136,9 @@ FiosType FiosGetSavegameListCallback(SaveLoadOperation fop, const std::string &f
 struct FiosNumberedSaveName {
 	FiosNumberedSaveName(const std::string &prefix);
 	std::string Filename();
+	std::string FilenameUsingNumber(int num, const char *suffix) const;
 	std::string Extension();
+	int GetLastNumber() const { return this->number; }
 private:
 	std::string prefix;
 	int number;