'magic' symlink support

Hi Folks,

   We've been experimenting with magic symlinks. The first patch
referred to below is a straight port of the patch in the netbsd
pr database:

http://www.netbsd.org/cgi-bin/query-pr-single.pl?number=1781

   For FreeBSD, the patch against -stable is at:

http://people.freebsd.org/~jwd/mlinks/freebsd-magic-patches


   The second patch applies on top of the first and provides
the ability to follow magic symlinks which are based upon values
in the user environment (_at_env_XXXX).

http://people.freebsd.org/~jwd/mlinks/env-magic-patches


   I have some very small patches against a few of the various shells 
since normalization of how the environment is kept is required
for this set.  I will get these up later this week.  Amoung other
things, this patch allows for some very interesting abilities within
the developement environment.  It is worth noting that this patch
also fixes the problem of "ps -e" showing stale environment variable
values.

   These still need to be ported/applied to -current.  Please give
them a try on -stable. Comments welcome.

-John