The comments for LoadLayoutOptions#layer_map, #cif_layer_map
and #dxf_layer_map have been updated to reflect the new status
of these properties (which have been methods). The tests
are updated accordingly (layer_map() -> layer_map).
The issue was: for MacOS/clang, the virtual format-specific
option structs had to be embedded in one compile unit (for RTTI).
In Windows this will lead to link errors since the DLL is not
reachable at build time for the generic reader/writer configuration in
the buddy tools.
The solution is to use GSI methods (provided for scripting) to
set the reader/writer options in a generic way that does not
require linking against the plugin DLLs.