Use array<> for RobotCenters
Simplify d1_matcen_info_read
Simplify D2X trigger upgrade code
Make padding value customizable
Use array<> for Triggers
Split out trigger_write

Conditional trigger_write is hard to read.
Use array<> for TmapInfo
Use array<> for Textures
Convert polymodel_read_n to call polymodel_read
Use array<> for Polygon_models
Read trigger structures carefully
Read matcen_info structures carefully
Use array<> for CloakingWalls
Read cloaking_wall structures carefully
Use array<> for Walls
Use array<> for ActiveDoors
Write active_door carefully