Rename ...write_bytes... to ...write_records..., that's what they do.
Move writer .h stuff into writer private .h file.
Change logic in writer to support both fifolog usage in FreeBSD and
Measured usage better, by always using an input buffer.
Various cleanups.
Quoth the man-page:
Fifologs provide a compact round-robin circular storage for recording
text and binary information to permanent storage in a bounded and pre-
dictable fashion, time and space wise.
Not yet connected to the build, but feel free to test & review.
