Test scenario: use wesnoth.debug_ai to access ai table

This means we can get rid of the global ai table definition.
Test scenario: Remove events that play through one turn at scenario start

The wesnoth.debug_ai table is now available from the beginning of the
scenario and for any side, no matter what controller= is set to.  This
does mean that trunk (or 1.11.5) is required now.
Update requirements to BfW 1.11.5
Test scenario: Correct order of commands in right-click option code

ai table needs to be defined before my_ai declaration
Update changelog