VFS_UNMOUNT(9) on FreeBSD

The text 3f29e160e0da, as FreeBSD 2.2.8-RELEASE, FreeBSD 2.2.7-RELEASE, FreeBSD 2.2.6-RELEASE, FreeBSD 2.2.5-RELEASE, FreeBSD 2.2.2-RELEASE shipped it.

unmount a filesystem

VFS_UNMOUNT(9) on FreeBSD now