(mult, player_coms): Command `mult' is disabled since 4.0.0 ('96), and

its code is obviously not in working order.  Remove.
(minmult, maxmult, configkeys): Unused configuration parameters,
remove.
(tradedesc): Remove code related to mult that had no effect.
(multread, commread, commwrite, commamt, commset, multset, commprice):
Dangerous, because code bypasses ef_read() & friends, remove.
(diss): Commodity cleanup uses the above, remove.  Command is disabled
and unlikely to work anyway.

src/lib/player/empmod.c

@@ -162,7 +162,6 @@ struct cmndstr player_coms[] = {
     {"move <c|m|s|g|p|i|o|b|f|r|u> <SECT> <NUM> <PATH|DESTINATION>", 1,
      move, C_MOD, NORM + CAP},
     {"mquota <SHIPS> <value>", 2, mobq, C_MOD, NORM + CAP},
-    {"mult [COUNTRY]", 1, mult, C_MOD, GOD},
     {"name <SHIPS> <NAME>", 0, name, C_MOD, NORM},
     {"nation", 0, nati, 0, VIS},
     {"navigate <SHIPS> <PATH|DESTINATION>", 1, navi, C_MOD, NORM + CAP},