They are only used under src/home/, but I want to add tests in test-libcrypt-util.c.
And the functions are almost trivial, so I think it is OK to move them to shared.
Also, let's move the glue for this to src/shared/ so that we later can
reuse this in sysemd-firstboot.
Given that libpwquality is a more a leaf dependency, let's make it
runtime optional, so that downstream distros can downgrade their package
deps from Required to Recommended.
Yu Watanabe