1.2.3

This is a production release of go-codec.

This optimizes decoding for zero-copy mode when decoding from a string or []byte.

With this mode, we see 50% reduction in allocation in both codecgen and normal execution,
and this gives performance better than other libraries (easyjson, json-iterator, etc)
while providing much more features and supported formats (json, cbor, msgpack, simple, etc).