Created "exposition" macros to describe operations performed on gBattleControllerExecFlags. Updated the battle engine internals to use them, to more clearly document how battle link communications actually work.
Replaced the BUFFER_A and BUFFER_B constants with the BATTLELINKMSGTYPE enum, which also identifies the "controller becoming idle" message type.
Named the task data for the link send task and the link receive task. Added macros to functions related to those tasks, for legibility.
DavidJCobb