fa.js: cosmetics.
fa.js: bt_nfa_matcher - also support nfae.
fa.js: bt_nfa_matcher - should also backtrack on premature end.
bt_nfa_matcher -> bt_nfae_matcher.
utils.js: cosmetics.
utils.js: sid_alloc - add support for prefix.
fa.js: nfae_maker - use separate alloc for temporary nodes.
fa.js: sort dict_keys() return values when necessary.