E1S5: minor prose, timing, and scrolling tweaks
E1S5: WML improvements

 * Use [filter_condition] instead of an [if] event
 * Scroll back to the primary unit after a mid-attack dialog event
 * Use MODIFY_UNIT for a single-atttribute change
E1S5: make saurians discuss undead on attack end, not attack
E1S5: improve saurian comment event handler

 * Don't scroll to the speaker.
 * Choose the speaker from a hex that's not adjacent or part of the
   action.