Make 'capnp decode' heuristically detect and warn when the wrong format flag (e.g. --packed, --flat) is used.
Extend 'capnp const' to support evaluating field default values as well as inner members of a value.
Remove some unused code.
Add test of capnp encode/decode/eval.
Fix bugs in format-detection heuristics.
Add segmented message to capnp test.
Improve readability of schema clasess a bit by making some union members into singleton groups.
Replace KJ_ARRAY_SIZE macro with a template function.
Rename non-group again, now to 'slot', which is much nicer.  Also introduce fixed lists as a third kind of field (but not implemented yet).
Actually, hold off on the fixed lists for now, needs more thought.
Add test of compiler's error-checking.
Add some missing type checks in dynamic.c++.
Make sure reading far pointers is thread-safe.
Update some todos
Fix problem in evolution-test.
Expand help text re: --packed.
Allow implicit convertion between StringPtr/Text::Reader and std::string.
Delete default construcrtor on builders, so that people don't incorrectly try to just declare a Builder on the stack and then start setting its fields.  Instead, a Builder can be explicitly assigned to nullptr, which makes it clearer that it isn't safe to use.
cerealization
Document capnp tool and constants.