* very efficient. I have improved the efficiency of the algorithm in two ways:
*
* (1) There are now two lists of items for each linetype. One list holds temporary
- * items, and the other list holds permenant items (ones which will expire).
- * Items which are on the permenant list are NEVER checked at all by the
+ * items, and the other list holds permanent items (ones which will expire).
+ * Items which are on the permanent list are NEVER checked at all by the
* expire_lines() function.
* (2) The temporary xline lists are always kept in strict numerical order, keyed by
* current time + duration. This means that the line which is due to expire the