Improve unions.  Members of a union are now scoped within the union, although they share ordinal space with the parent struct.

Get rid of redundant ErrorReporter that goes in ReaderOptions.  Registering an ExceptionCallback is a better approach.

Replace most CAPNPROTO_ASSERTs with the new logging/error macros.  Also add a SYSCALL macro and use it.  Also add commentary.

Refuse to read messages with excessive segment counts or messages whose total size exceeds the traversal limit, before allocating any space.  This is important for security.

Update far pointer implementation to match spec.  Also adjust the spec slightly so that you can tell whether a far pointer is a double-far before you dereference it.

Fixed typo in "operation"

Supports choosing output languages on the command line.

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.

Make enum syntax match docs, make enum lists work correctly, add enum tests, enforce maximum ordinals on enum values and interface methods, change the maximum field ordinal to 16-bit to match docs (now all ordinal limits match).