> introduce accessors, introduce a build macro to mangle fields so code building against these fields generates warnings, and then when code has been sufficient

> introduce accessors, introduce a build macro to mangle fields so code building against these fields generates warnings, and then when code has been sufficiently ported, pull the rug, remove the accessor macros. Hear hear. Exactly what Carbon did to ease porting from InterfaceLib. * CarbonAccessors.o * #define OPAQUE_TOOLBOX_STRUCTS 1 * #define ACCESSOR_CALLS_ARE_FUNCTIONS 1