wizidentify suppress unnecessary prompt; allow individual items for perm ID

Don't display the selection to identify all items if there are none.

Complete an item marked ToDo in cmd.c: allow selection of one or more
particular items to permanently identify rather than just all or nothing.

src/cmd.c

@@ -652,7 +652,6 @@ wiz_identify(VOID_ARGS)
            it doesn't matter whether the command has been remapped */
         if (display_inventory((char *) 0, TRUE) == C('I'))
             identify_pack(0, FALSE);
-        /* [TODO?  if player picks a specific inventory item, ID it] */
         iflags.override_ID = 0;
     } else
         pline("Unavailable command '%s'.",