Commits
Xi Ge committed d0e176810f4
[Serialization] Serialize doc comments for extensions. Need this for rdar://25157796 We did not serialize them because getting USR for extensions is tricky (USRs are usually for value decls). This commit starts to make up an USR for an extension by combining the extended nominal's USR with the USR of the first value member of the extension. We use this made-up USR to associate doc comments when (de)serializing them.