feat: creating and removing empty directories

[wassup05]

User facing functions added are

• make_directory (path, mode, err) (mode argument only for Unix systems)
• remove_directory (path, err)

1. Both of them support relative paths and on Windows, paths involving either / or \.
2. They bind to the CRT functions mkdir, rmdir, _mkdir, _rmdir on Unix and Windows respectively.
3. A binding to strerror has been included as a private helper to provide helpful error messages.
4. state_type is used for error handling.

Side note:
make_directory could have a logical argument recursive which would work like mkdir -p but that would require path manipulation especially dir_name from #999

Do let me know your thoughts.