use "Metis_" prefix rather than "Metis" structure;
the prefix can then be used not only for structures but also signatures and functors. A few other changes were made to the script, to eliminate the need for "metis_env.ML".
use "../settings.ML";
use_thy "Tree";
use_thy "Tree2";
use_thy "Plus";
use_thy "case_exprs";
use_thy "fakenat";
use_thy "natsum";
use_thy "pairs";
use_thy "Option2";
use_thy "types";
use_thy "prime_def";
use_thy "simp";
use_thy "Itrev";
use_thy "AdvancedInd";
use_thy "appendix";