Cleanup to allow use of most functions when linking the library, including mounting and creating filesystems

Remove unused import causing lint

futimens: do not require O_RWONLY/O_RDWR

Make it not an error to open a directory without O_DIRECTORY or O_STAT

POSIX says this should work, and some software seems to rely on that.

Remove unneeded uses of 'mut'

This seems to be a warning with the latest Rust, and an error due to #![deny(warnings)]

Avoid corrupting free node

Directory symlinks

fuse: allow setting mtime to earlier time

fuse: Fix readdir when directory does not fit in buffer

Require same uid as owner to unlink, not write permission

Do not fail due to file permissions on creation

Matches Posix.

Make fcntl not clobber access mode