A cleanup.

sql/sql_parse.cc:
  ALTER TABLE should not be affected by DONT_ALLOW_SHOW_COMMANDS
  (a bug that's there since version 1.1)

sql/sql_parse.cc

@@ -3045,11 +3045,6 @@ mysql_execute_command(THD *thd)
 
   case SQLCOM_ALTER_TABLE:
     DBUG_ASSERT(first_table == all_tables && first_table != 0);
-#if defined(DONT_ALLOW_SHOW_COMMANDS)
-    my_message(ER_NOT_ALLOWED_COMMAND, ER(ER_NOT_ALLOWED_COMMAND),
-               MYF(0)); /* purecov: inspected */
-    goto error;
-#else
     {
       ulong priv=0;
       if (lex->name && (!lex->name[0] || strlen(lex->name) > NAME_LEN))
@@ -3115,7 +3110,6 @@ mysql_execute_command(THD *thd)
       }
       break;
     }
-#endif /*DONT_ALLOW_SHOW_COMMANDS*/
   case SQLCOM_RENAME_TABLE:
   {
     DBUG_ASSERT(first_table == all_tables && first_table != 0);