Treat symlinks as first class citizens with their own uid/gid rather than
as shadows of their containing directory. This should solve the problem
of users not being able to delete their symlinks from /tmp once and for
all.

Symlinks do not have modes though, they are accessable to everything that
can read the directory (as before). They are made to show this fact at
lstat time (they appear as mode 0777 always, since that's how the the
lookup routines in the kernel treat them).

More commits will follow, eg: add a real lchown() syscall and man pages.