Enable Blowfish / bcrypt

It seems like the very efficient Blowfish hashing algorithm is not enabled by default. I am forced to use this algorithm due to existing user accounts I want to migrate.

Is there any way to enable it? It should be provided in `libxcrypt` but it looks like the image ships `libcrypt` (no `x` in the middle). Another way to enable it would be including https://github.com/wclarie/openldap-bcrypt .