Postgres native support was added in FreeSWITCH 1.2.5.
libpq and the associated dev packages are required
If you have installed a later version of PostgreSQL from a source other then your distro's repositories, and its installed to a non-standard location such as /usr/pgsql-9.5 you will need to adjust your PATH and/or PKG_CONFIG_PATH environment variables to properly locate either pg_config or libpq.pc
Adjust your PKG_CONFIG_PATH and PATH as required for your platform.
host vs hostaddr
'hostaddr' ONLY takes a numeric ip address and will not resolve a hostname. Use 'host' for a DNS hostname. If you specify both 'host' and 'hostaddr' settings, 'hostaddr' takes precedence.
For PostgreSQL, FS strips the 'pgsql://' from the DSN and passes the remainder of the string directly to libpq's PQconnectdb() for connection to the database. See the libpq docs for further information on creating a proper connections string.
Once you have PostgreSQL configured in the core, you can connect to the database and ensure you have tables, like the following.