[PATCH 02/14] Add support for a generic wal reading facility dubbed XLogReader

Features:
- streaming reading/writing
- filtering
- reassembly of records

Reusing the ReadRecord infrastructure in situations where the code that wants
to do so is not tightly integrated into xlog.c is rather hard and would require
changes to rather integral parts of the recovery code which doesn't seem to be
a good idea.

Missing:
- "compressing" the stream when removing uninteresting records
- writing out correct CRCs
- separating reader/writer
---
src/backend/access/transam/Makefile | 2 +-
src/backend/access/transam/xlogreader.c | 1032 +++++++++++++++++++++++++++++++
src/include/access/xlogreader.h | 264 ++++++++
3 files changed, 1297 insertions(+), 1 deletion(-)
create mode 100644 src/backend/access/transam/xlogreader.c
create mode 100644 src/include/access/xlogreader.h