Namecache status report #2

[Gleb Kurtsou]

I've commited initial dircache version. It's still very much 'work in
progress', only most basic functionality is available. Now I'm working
on stabilizing it and adding missing bits (no cache entry expiration
expected yet). I'll also try to add dircache support to msdosfs and then
look at stacked filesystems. I've spent too much time researching
namespace/several parents per entry issues at the beginning, thus
starting rather slowly.