Deprecation support

[Yuxuan Wang]

I noticed that there are some recent activities on implementing deprecation
support in languages. I'd like to implement it in go, but I'm wondering if
there is a "formal" definition/spec on what are the ways to mark
types/fields as deprecated in thrift IDL? Or should I just treat the
deprecated.thrift file attached to
https://issues.apache.org/jira/browse/THRIFT-5781 as an exhaustive list we
need to support in languages?