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