fsync_range and O_RDONLY

[David Holland <dholland-tech%netbsd.org@localhost>]

Last year, fdatasync() was changed to allow syncing files opened
read-only, because that ceased to be prohibited by POSIX and something
apparently depended on it.

However, fsync_range() was not also so changed. Should it have been?
It's now inconsistent with fsync and fdatasync and it seems like it's
meant to be a strict superset of them.

-- 
David A. Holland
dholland%netbsd.org@localhost