Create parent dirs for useradd -m

Create parent dirs for useradd -m

Equivalent of `mkdir -p`. It will create all parent directories.
Example: `useradd -d /home2/testu1 -m testu1`

Based on https://github.com/shadow-maint/shadow/pull/2 by Thorsten Kukuk
and Thorsten Behrens which was Code from pwdutils 3.2.2 with slight adaptations.

Adapted to so it applies to current code.