changes:
Updated the documentation in human update_icons a bit.
Renamed overlays_standing to overlays_raw to better describe what it is.
Nuked more compound overlays.
Ghosts now use appearance copy to copy their old mob (Fixes#3135)
Layer defines are now space-aligned instead of tab-aligned.
Renamed SURGERY_LEVEL to SURGERY_LAYER like the other layer defines.
Fixed a potential bug where belt overlays may have not cleared in certain cases.