log_newpage is used by many index types, as well as for heaps. But for
historical reasons, it's always been in heapam.c, as part of the Heap
resource manager.
We now have a new record type that just contains a full page image,
XLOG_FPI, used to log hint bit updates when checksums are enabled.
This is a bit silly, so barring objections, I'll commit the attached
patch that moves log_newpage to xlog.c, and makes it use the XLOG_FPI
record format.
- Heikki