When encountering a symlink, we abandon the custody chain we've been working
on and start over with a new one (by recursing into a new resolution call.)
Caching symlinks in the custody model would be incredibly difficult to get
right with all the extra invalidation it would require, so let's just not.
The current working directory is now stored as a custody. Likewise for a
process executable file. This unbreaks /proc/PID/fd which has not been
working since we made the filesystem bigger.
This still needs a bunch of work, for instance when renaming or removing
a file somewhere, we have to update the relevant custody links.
A custody is kind of a directory entry abstraction that represents a single
entry in a parent directory that tells us the name of a child inode.
The idea here is for path resolution to produce a chain of custody objects.
Also run it across the whole tree to get everything using the One True Style.
We don't yet run this in an automated fashion as it's a little slow, but
there is a snippet to do so in makeall.sh.
