Summary:
This change adds a `RecordPrinter` type which does some basic text
serialization of the FDR record instances. This is one component of the
tool we're building to dump the records from an FDR mode log as-is.
This is a small part of D50441.
Reviewers: eizan, kpw
Subscribers: mgorny, hiraditya, llvm-commits
Differential Revision: https://reviews.llvm.org/D51672
llvm-svn: 341447
