This addresses two related issues:
- Units visibly garrisoned on gates keep the gate open.
- Units visibly garrisoned on entities keep their pathfinding blocker
flags.
Remove the block-movement flag from visibly garrisoned entities.
Keep a list of entities that cannot move and thus should not count
towards gate-opening logic.
Packing logic is kept separate: it is more related to entities having
'alternate forms' with different capabilities than being currently
incapable of moving.
Based on work by temple
Comments by: Freagarach
Tested by: Nescio
Fixes#2679Fixes#5151
Differential Revision: https://code.wildfiregames.com/D1418
This was SVN commit r23710.