bsd-family-tree: Sync with FreeBSD.

* DragonFly 4.0.1
* FreeBSD 10.1
* NetBSD 6.1.5
* OpenBSD 5.6
mountd - Module load handling

- Change the way the 'nfs' module is loaded.
- Use getsysctlbyname() to get vfs.nfs.nfs_privport

Taken from: FreeBSD SVN 83687