Enable lua string library (int to string, string to int and some other useful things)

git-svn-id: svn://pulkomandy.tk/GrafX2/trunk@1588 416bcca6-2ee7-4201-b75f-2eb2f807beb1

src/factory.c

@@ -1001,7 +1001,7 @@ void Run_script(char *scriptdir)
   luaopen_table(L);
   //luaopen_io(L); // crashes on Windows, for unknown reason
   //luaopen_os(L);
-  //luaopen_string(L);
+  luaopen_string(L);
   luaopen_math(L);
   //luaopen_debug(L);