VFS_SYNC(9) on FreeBSD

The text ddaa26e65e8a, as FreeBSD 4.4-RELEASE, FreeBSD 4.3-RELEASE, FreeBSD 4.2-RELEASE, FreeBSD 4.1.1-RELEASE, FreeBSD 4.1-RELEASE, FreeBSD 4.0-RELEASE shipped it.

flush unwritten data

VFS_SYNC(9) on FreeBSD now