* Removed reflection and other extraneous things from the core library.
* Added missing files and ran buildifier.
* New CMakeLists.txt.
* Made table its own cc_library() for internal usage.
- Foo_parsenew() -> Foo_parse().
- parse function takes plain (const char*, size_t) instead of
upb_strview. The latter is mainly useful for strings inside
message objects.
upb_msg was trying to be general enough that it could either live in
an arena or be allocated with malloc()/free(). This was too much
complexity for too little benefit. We should commit to just saying
that upb_msg is arena-only.
I also ripped out the code to glue upb_msg to the existing
handlers-based encoder/decoder. upb_msg has its own, small, simple
encoder/decoder. I'm trying to whittle down upb_msg to a small
and simple core.
I updated the Lua extension for these changes. Lua needs some more
work to properly create arenas per message. For now I just created
a single global arena.