"sshfs -o vsock=CID:PORT" will cause sshfs to connect directly to the
given vsock, bypassing ssh, and allowing high performance sshfs mounts
of a VM guest.

Implement connect to vsock.

remove README.rst file since README.md file exists

Uncached and cached results for readdir were inconsistent -- the former
returned correct stat info for directory entries while the latter
didn't. That's because only names of entries were saved in cache without
stat info. In turn this leads to issues like
junegunn/fzf#3832 since directory traversal
library (https://github.com/charlievieth/fastwalk in this case) relies
on proper stat info returned by readdir. Hence when unchached result was
returned it gave proper outcome, while with cached result it was wrong.

Cache stat info next to entry name to fix the issue. While file
attributes are saved in cache already, they use full path as key. To
avoid potentially plenty of allocations, string copying and cache
lookups to get each attr, let's keep a copy of stat struct independently
to be on the fast path.

Fix memleak in cache after readlink

Fill stat info when returning cached data for readdir