Move iff_read_animbrush array<unique_ptr<grs_bitmap>> down
Use symbolic *_none constants for -1
Use magic type for wall magic constants
Combine EVENT_UI_DIALOG_DRAW blocks
Remove unnecessary padding in segment sides
Move d2x-rebirth/main/segment.cpp -> similar/main/segment.cpp
Use new serializer for writing segment side wall/tmap
Switch d_event subclasses to C++ inheritance
Pass d_event arg by const&
Remove unnecessary UI_GADGET* casts