Test build 20: 2.4-fork6 — the bank claim honours builds 17–18; delete, move, tidy, name banks

Install THIS over build 18, not build 19: a device that loaded its twelve banks on 18 keeps every one of them (18's own record is honoured); from 16 or 17, banks 1–4 refill themselves and the rest come up empty. The editor's DX7 card can now delete a voice, move one to another bank, tidy a bank and name banks (names live in the editor and in a backup file). Otherwise as test build 19. Not a SLOOP release.