non critical mounts

[[LoN]Kamikaze]

Failing NFS mounts with the -b option take a lot of time,
because they fork AFTER an attempt has failed. And that
normally takes a lot of time.

So I have written that patch, which fixes the behaviour
by forking even before the first attempt is made.
http://www.freebsd.org/cgi/query-pr.cgi?pr=103089

But now I wonder weather it wouldn't be better to introduce
an option like nocrit for non critical mounts in sbin/mount
that generally forks mounts with that option into the
background. It would be useful for all kinds of replaceable
drives and network shares. Especially in an ever changing
environment such as a Laptop.

Now why not amd you say, the answer being that it costs
significant CPU time when using such a mount. That does
not matter on an optical drive, but when you want to build
the world on an external HD, it makes a difference.