BUG #14797: It's not safe to use MD5

The following bug has been logged on the website:

Bug reference: 14797
Logged by: Dmitriy Davydov
Email address: dmitriy(dot)davydov(at)deiteriy(dot)com
PostgreSQL version: 9.6.5
Operating system: CentOS
Description:

Hello.
Postgresql 9.6.5 , by default , database user passwords are stored as MD5
hashes (18.8 Encryption Options.
http://repo.postgrespro.ru/doc/pgsql/9.6.5/en/postgres-A4-fop.pdf) At the
moment, it's not safe to use MD5.
Unfortunately, Rolename is used as the salt.
(src/backend/commands/user.c
if (!pg_md5_encrypt(password, rolename, strlen(rolename),
encrypted_password)) )
This is also unsafe.
Payment Card Industry (PCI) Data Security Standard requires the use of hash
functions described in FIPS 180-4, such as SHA-256 and SHA-512.
Please make changes in future versions.