A compatibility layer is provided to ease migration.

The project file still only compiles a test binary, but it should be easy to separate out a library project from here.

Thanks again to Bryan Boreham <bjboreham@gmail.com> for much help getting this working.

Extended discussion:
https://groups.google.com/d/msg/capnproto/lRlWBOglQv4/8-Qo96AcZQIJ

For portions currently copyright by Kenton (most of it), transfer copyright to Sandstorm Development Group, Inc. (Kenton's company).

The license change is practically meaningless, as MIT and BSD 2-clause are legally equivalent. However, the BSD 2-clause license is sometimes confused for its ugly siblings, BSD 3-clause and BSD 4-clause. The MIT license is more immediately recognizeable for what it is.

Rémy Blank and Jason Choy (the two non-trivial contributors) are on record as approving this change:

https://groups.google.com/d/msg/capnproto/xXDd2HUOCcc/gbe_COIuXKYJ

I decided that consistent output across platforms is an important property, worth sacrificing a little bit of performance on MIPS.

Eliminate the concept of imbuing messages in favor of the simpler concept of setting a cap table directly on MessageReader / getting one from MessageBuilder.  This eliminates capability-context entirely.  This was made possible by the earlier change which moved capabilities to a separate table rather than storing CapDescriptors inline, but I didn't realize it at the time.

Factor Pointer{Reader,Builder} out from {Struct,List}{Reader,Builder}.  Will make it easier to deal with Object fields.

Mass rename 'reference' -> 'pointer'.  Been meaning to do this for a while -- all the documentation talks about 'pointers', not 'references'.

Update implemented pointer format to match docs:  Don't store field count in struct pointers because it isn't needed.  Instead extend data and pointer section sizes to 16 bits, which should be enough for anyone.  Also, store offsets from the end of the pointer rather than the beginning, because this makes it possible for them to be zero, which compresses better.  In particular, the root reference will always have a zero offset, so this will shave a byte off of very small packed messages.

Rename the 'Message' interfaces to Arena and make them internal.  Make a new, intuitive 'Message' interface for creating / reading messages.